I read the following “Torah encourages us to enhance and beautify a mitzvah as much as possible.”
1. What exactly is a mitzvah? I get the impression it’s a command, but perhaps more of an obligation.
2. Where is this encouragement in the Torah?
You are correct that a Mitzvah is an obligation. It is also sometimes used to refer to a good deed. E.g., it’s a mitzvah to help the poor. Beautification of a Mitzvah is based on the verse (Exodus 15:2), “this is my G’d and I will exalt Him.” Exalt means revere and make beautiful.