Here's why:
* Gerund: "Drawing" is a gerund, which is a verb form ending in "-ing" that acts as a noun.
* Subject: The subject of a sentence is the person, place, thing, or idea that performs the action of the verb.
* Verb: "is" is the verb in the sentence.
So, the sentence is saying that the act of "drawing" is the speaker's favorite thing to do.