This map is in bnet under sheep wars
In this map your goal is to kill the enemy HQ. To do that, you need sheep. To get sheep, you need buildings. Your buildings provide sheep every 3 seconds infront of your HQ.
You can research higher teir sheep. Teir 3(final) sheep are upgradeable in range and damage, range could be very much useful, alowing instead of 1 row of melee sheep to attack, it could allow 2 to maybe 3 rows when fully upgraded, allowing you to obliterate your enemy if they have not researched enough.