Years ago, Major League Baseball instituted Competitive Balance rounds to be inserted into the usual draft order as a method to provide the 10 lowest revenue teams (and 10 smallest market teams) with a little extra pep in their draft step. Competitive Balance Round A falls immediately after the first round, while Round B comes immediately following the second.
Not only does it give these clubs an extra pick near the top of the draft, it factors into their overall draft bonus pool amounts, too - in other words, the pick is nice, but it could well be used as a way to go overslot with other picks to sign away players who otherwise might end up taking the college route.