Simple future has two different forms in English: "will" and "be going to." Although the two forms can sometimes be used interchangeably, they often express two very different meanings. These different meanings might seem too abstract at first, but with time and practice, the differences will become clear. Both "will" and "be going to" refer to a specific time in the future.
Future perfect has two different forms: "will have done" and "be going to have done." Unlike simple future forms, future perfect forms are usually interchangeable.