<< (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.