Token burning entails permanently erasing from existence a portion of the entire quantity of a certain token that is currently in circulation, or in other words, it entails lowering the Supply.

You are right friend, token burn is used to destroy coins permanently through the null address and no asset that enters can leave again. The primary aim of this is to reduce the supply of the asset for improved value in the market.

Burning of steem is a novel method used by blockchain organizations to reduce the amount of steem currency in circulation.

Yes, they do it to reduce supply of their tokens to have more value and also to attract more investors to their project.