The question your teacher is asking is this: How do the pigs use language to get what they want? In other words, how do they speak cleverly to convince others to do everything just the way the pigs want it done.
For example, the pigs want the animals to hate humans. So the pigs come up with an easy slogan to remember "Four legs good, two legs bad." It is so easy to remember, the other animals can't forget it and will eventually start to believe it.
The pigs also try to make work sound more interesting so that the animals will want to work harder. Instead of just "providing wool" or "giving eggs", the sheep are part of the Winter Wool Movement and the hens are part of the Egg Production Committee. This makes them feel more important.
The pigs use rhetorical questions to make the other animals agree with them. When the animals seem like they won't work too hard, Squealer ask "You don't want Jones to come back, do you?" This makes it seem like the farmer will come back if the animals don't work their hardest. Its a threat. It isn't true, but it convinces the animals through fear.
Finally, the pigs control which animals learn to read. This way, the pigs can claim to know more and they can sound more important because they can read things and their vocabulary is bigger.