لابس is the اسم الفاعل (active participle) of the root verb لبس

يلبس is the masculine 3rd person singular (present tense: الأفعال المضارع ) form of the root verb لبس

REFERNCES:

http://allthearabicyouneverlearnedthefirsttimearound.com/p2/p2-ch2/active-and-passive-participles-forms-i-and-ii/

http://arabic.desert-sky.net/g_vforms.html

Five Colleges Language Video on Ism Fa2il https://www.youtube.com/watch?v=QucykPvo2ec