Here’s what the baby site sez Jake will be doing:

Coos are your baby’s way of expressing delight, as well as exercising his vocal cords. You can carry on a “conversation” with your baby now. When he gurgles or coos, say something brief or coo back at him. Then wait for him to “say” something back to you. This kind of conversational turn-taking may not sound like much to you now, but it’s actually the beginning of learning how to talk.

He’s already doing most of this right now. More later!