Difference between Google search commands and search operators

Well,. there are too many type of searches there, they are:

Broad search: your KEYWORD
Phrase search : your "KEYWORD"
Exact search : your [KEYWORD]

and you can also use some operators and this search is called as Boolean search...

Google supports different advanced search operators in order to make your search experience more satisfying, faster and easier to perform. Those operators have special meaning to Google search engine and are interpreted as commands in search algorithm. You can use those operators to find desired file types, links, and in general any kind of information. To use them, you simply need to add certain search operator before searched query in standard search box.