What is the difference between these two japanese words?

the root verb in kitteimasu is Kiru which means to wear (for upperbody only like tshirts and coats). Kiru is a cl one verb so when you change it to The boy is wearing (right now) a tshirt then you would change it to kitteimasu. Haiteimasu on the other hand, has the root verb Haku which means to wear, but only with the lower body. So you wouldn't say Tshatsuwo haitemiasu. That is incorrect. You would say jeanswohaiteimasu or kutsuwo haiteimasu. So to summarize it: they both mean to wear, but kiru is on upper body, and haku is for lower body :)