The search is done via Google, some elements available:

« »: quotation marks allow you to search for an exact phrase.

-: the minus sign allows to exclude a term.

~: the tilde allows to include the synonyms of the term.

AND: excludes pages that do not contain the specified terms.

*: the asterisk is often used to know the entirety of a sentence or an expression.

OR: the operator can search for a term, or another.

More details: Here and Here