Binding takes place at the active site. This is the site where the catalytic reaction occurs and products are formed. The geometry of the substrate is complementary to the active site to facilitate bonding.
Each type of enzme has a uniquely shaped active site. The substrate or reactant molecule fits in the active site. The binding of the substrate to an active site causes the enzyme to change shape slightly (induced fit). Some enzymes do has an area similar to the active site, which is the allosteric site which allows a noncompetitors inhibitors to enter it.