Vovin's tek explains itself pretty well. To add to that you could find out what polar/non-polar means, what a solvent is, what it means to salt something, what it means to freebase something, why liquids of different density separate, and whatever else is still a relevant mystery.
I will explain it as well.
There are many types of DMT one can end up working with, DMT-Citrate, DMT-Phosphate, DMT-Acetate, DMT-Tarate, DMT-Fumarate, DMT-Hydrochloride, DMT-Asorbate, DMT-Malate, DMT-Tannate, DMT-Sulfate, DMT-Borate, DMT-Formate, on and on and on. These are all salts of DMT, a very different thing from DMT you would smoke. The citrate refers to citric acid, the phosphate refers to phosphoric acid, on and on. pH in laymen's terms in a measure of acidity or alkalinity. Acids have a pH below 7, while alkalines (also called bases) have a pH above 7. pH scale ranges from 1-14.
DMT found in MHRB is in a salt form, however no one knows which salt of DMT it is. All salts of DMT are very soluble in polar solvents. There are many polar solvents with varying levels of 'polar-ness,' some examples of polar solvents are water and alcohol. Water is almost always used because of its availability and cost. An important point here is that all the salts of DMT have different solubility in say... water as the polar solvent. Data isn't available as to which salt of DMT is the most soluble in water, so don't concern yourself with that. If you could, you would want to know which salt of DMT is most soluble in water because that means that more DMT can be held in less water. You want to use less water because it simply makes everything easier by their being less to work with.
In an Acid/Base tek found on the DMT Nexus Wiki, the idea behind that is to take whatever salts of DMT that exists in MHRB naturally and convert it all into a salt that is known to us. To do this you saturate the MHRB in water, a polar solvent. Again because the salts of DMT are soluble in water, they will migrate from the bark and dissolve into the water. There is a maximum point at which no more salt of DMT can be dissolved into the water, here again is why you would want to know which had the highest solubility. Please do not make the mistake of adding more water to your bark in hopes to get more DMT out of it.
Once you have the polar solvent covering the MHRB, you can raise the pH with an acid. In my experience acids sold in liquid form are far superior to using dry salted acids. I recommend liquid phosphoric acid because it has no odor, is very potent while being food safe if you buy that quality, and one bottle will last an extremely long time, and it is safe to use on many surfaces and containers that hydrochloric acid is not. For cooking containers I recommend a ceramic or stoneware crock pot. Glacial Acetic Acid or it's diluted impure version 5% acidity white vinegar would be my second choice, but phosphoric still wins as I personally hate the smell of vinegar. Again for repetition's sake to use Acetic acid would form DMT-Acetate. The acidity of the polar solvent should be around pH 4. Obviously you need a way to measure pH, Ebay is your friend here.
The other reason for an acid cook is to break down the MHRB cell structure using the acid and free more DMT from the bark into your polar solvent. In a Straight-To-Base tek the MHRB is saturated with lye and allowed to sit for several days. Lye breaks down the cell walls of the MHRB, and an acid cook is avoidable. Acid cooks are said to produce a cleaner product, and I tend to agree. They are also faster than waiting a few days.
Many acid cooks are performed to insure that all available DMT has been dissolved into the polar solvent. At this stage you have a polar solvent saturated with salts of DMT. If one wished to remove some of the plant oils which can contaminate the end product they would add a non-polar solvent at this stage. Salts of DMT may be soluble in polar solvents, but they are extremely insoluble in non-polar solvents. Typically the more aggressive of a non-polar solvent the better for removing plant oils. Toluene and Xylene are suitable choices. The non-polar solvent is allowed to sit for some time, then removed and the process is repeated several times to remove all the plant oils.
It is important to note that excess heat at any stage of an alkaloid extraction can ruin the end product. Alkaloids are not the sturdiest of molecules, and excessive oxidation from heat will ruin the end product.
Once the non-polar solvent has been thoroughly removed from the polar solvent, you then proceed to freebase the DMT. A freebase is a pure form of an amine, as opposed to its salt form. Freebase DMT is soluble in non-polar solvents, while salt DMT is soluble in polar solvents. The process of freebasing DMT is very simple, raise the pH above 10.whatever-it-is (just go above pH 12 it will not hurt it any) using a strong alkaline, and the DMT will convert to freebase. If lye was used as the strong base the lye (sodium hydroxide) will convert into a salt of sodium that is soluble in polar solvents. Since Freebase DMT is not soluble in polar solvents, it can dissolved into a non-polar solvent at this stage. Non-polar solvent is added, usually naphtha, heptane, dichloromethane, or hexane, and agitated for 10-15 minutes. This process is repeated to ensue that all freebase DMT is dissolved into the non-polar solvent.
The non-polar solvent and polar solvent will not mix, they will separate and form two distinct layers. Less non-polar solvent is used than polar solvent, so it is easier to remove the non-polar from the polar. Naphtha, hexane, and heptane will collect above water, while DCM will sink to below the water. Once the non-polar solvent is removed it can either be evaporated to leave behind the DMT, or it can be placed into a freezer. The solubility of freebase DMT in naphtha or heptane decreases as the temperature of the non-polar solvent decreases. Please do not follow the logic that the hotter it gets the more soluble it becomes, as you will oxidize your DMT can ruin the product if it is too hot. This is technically true however, and while more DMT can dissolve into warmer solvent, impurities become more soluble too.
Once the solvent reaches a cold enough temperature for a long enough time the DMT can no longer stay dissolved and it will fall out of the solution. Crystalline structures of DMT will begin to form. The DMT is then recovered mechanically by pouring off the solvent while it remains cold and letting the DMT air dry.
That's the basics! You will get the hang on it once you read this and then go back and read the steps of a tek. It will pair the esoteric with the practical 'doing' in your mind, vovin's is a good tek because it has pictures as well.