Google has decided that if someone sends an email to a Gmail address that is the same as yours, except for a period or few, it was meant for you; and they relay it to your mailbox.
In other words, if I have an address cilias@gmail.com (which I do not), and someone sends a message to c.ilias@gmail.com (or cil.ias or cili.as or ci.lias or cilia.s or c.i.l.i.a.s, etc.), and none of that Gmail address does not exist, the message will arrive in my cilias@gmail.com account.
All this does is increase my spam.