What is difference about [] and <> that in aws cli help message?

Question

I enter this command:

aws help

Then I saw this line:

aws [options] <command> <subcommand> [parameters]

I know all of [] and <> are represent about let me type some words replace it. But what is the difference between [] and <>?

Answer 1

Arguments in angular brackets (<>) ae required, arguments in square brackets ([]) are optional. E.g., you have to have a command and a subcommand, but options are, well, optional.