M.B.
Sounds like he is coming along very nicely.
Receptive language (what we say to them, and what they understand) always develops much faster than expressive language (what they say to you).... it takes quite a while to "train" the muscles of the tongue and mouth to form words properly.
It really is amazing what little ones understand! We often forget they are like a little sponge, soaking up so much everyday.