<< (double less-than signs) means that the search string preceding the signs should also precede the search string following it. Searching for Mari << Anne will return "Mari Anne" and not "Anne Mari".
() (parentheses) are used to group your returns.
E.g. Marianne | (Mari << Anne), will return both "Marianne" and "Mari Anne". The search Marianne | Mari << Anne will only return "Mari Anne" and "Marianne Anne", if someone were to be named that.