"C'est" is a French expression that translates to "it is" or "this is" in English. It is commonly used to introduce or identify something, such as a person, object, or idea. For example, you might say, "C'est un livre" to mean "This is a book." In addition to identifying, "c'est" can also express opinions or feelings. For instance, "C'est magnifique" means "It is magnificent." This versatility makes "c'est" an essential part of everyday French conversation, helping speakers convey information and emotions effectively.