Many molecular hunters prefer ligand based similarity searching methods as a virtual screening tool , to identify those structures that are most likely to bind to a drug target, typically a protein receptor or enzyme or search for similar structures by pharmacophoric properties , 3D shape , scaffolds or in context of graphs similar graphs.
In graph theory, a clique is a subset of vertices that form a complete subgraph, meaning that every pair of distinct vertices in the clique is adjacent (connected by an edge). A maximum clique (or max clique) is a clique of the largest possible size in a given graph. This means that it is not contained within any larger clique. A maximal clique is unique in its neighborhood but might not be the largest in the overall graph. If you want to understand graph concepts there is nice channel at youtube.