Docking refers to the process of positioning a small molecule (ligand), such as a chemical compound that could potentially be used as a drug, on a protein's surface. However, some ligands have a greater affinity for a given protein (receptor) than others and finding the exact position (aka pose) during simulated docking on a computer requires that the computer try many positions before the best position is found. Best in this context means the position where the ligand binds with the lowest energy (measured in kcal/mol). And we must try thousands (or even millions) of ligands to find the best ligand. This is a bit like trying to find a key that fits an unknown lock. Try enough keys and one might fit.

Virtual screening refers to the process of docking many chemical compounds with a target protein in silico to eliminate large numbers of compounds from further consideration and ranking remaining compounds from most to least promising (Kitchen et al., 2004).

This short youtube video from 2010 illustrates docking.

These Autodock Vina tutorials are from: 2018 and 2020 .