A "format" is an arrangement of things, a "pattern".. For example, a CV usually looks a certain way. A "form" is a document in which there are spaces left blank in which you enter information. For example, to apply for a passport you fill out a form. "Form" in particular has other meanings, so I can guessing the usage you are looking for in which they are similar. The primary meaning of "form" is the composition and shape of some object.