Cholinergics are compounds that, after consumption, increase levels of acetylcholine in the brain.
Increased acetylcholine can lead to improvements in muscle power and contraction, as well as possibly increased reflexes and capacity to learn.
Cholinergics can be subdivided into compounds which produce Choline in the brain which is the substrate for acetylcholine (in which increasing substrate increases synthesis of acetylcholine) or compounds which act on the enzyme of acetylcholine creation (Choline acetyltransferase) and increasing its actions, or by acting on the enzyme of degradation (acetylcholineesterase) and preventing it from degrading choline. Both of which are mechanisms of increasing choline in the brain independent of substrate concentration.
Many cholinergics have individual benefits outside of the classification of cholinergic as well, such as the ability for DMAE to remove lipofuscin build-up in neural tissue and the ability for Choline to reverse or aid fatty liver disease.