Leo is a Kwami, who is connected to the Lion Miraculous and currently resides with Lionel Oshiba . Leo is a lion-like Kwami and is typically understanding, loyal, charasmatic, and sometimes worrisome, which he mostly chastises Lionel when he's fighting recklessly as Lionheart.
Leo is often described as different out of all Kwamis as well as Tikki, Plagg and the other Miraculous Kwamis. Having lion-like features and a rough and fierce sounding voice may have them thinking he is a tough and sometimes arrogant personality. But in reality, Leo is very understanding, loyal, and charasmatic.
He is also sometimes a bit strict, thus scolding Lionheart for often being a bit wreckless when it comes to battles and becomes very worrisome when he sees Lionel not being his usual self and act all 'motherly' towards him, much to his annoyance but he knows that Leo cares about him and wants to see him having positive thoughts instead of negative.
Leo's favorite snack is macaroons and Lionel often gives him the one Marinette makes in her family bakery.