You can modify the shape of your polygonal meshes using features called deformers. Deformers let you modify the individual components of a mesh at a global level so you don’t have to modify each component individually. Deformers can also be used to animate the shape of an object. For example, using a lattice deformer you construct a cage-like box or lattice that surrounds the object you want to modify.
You then modify the lattice which then modifies the object. Maya has many types of deformers available-: blend shape, lattice, cluster, nonlinear, sculpt, soft modification and so on. For more information on the various types, see the Deformers guide.