वह करता है is in the simple present tense (i.e. He does it)

वह कर रहा है is in the present continuous tense (i.e. He is doing it)

 Hope this helps! :-)

"He do/does" --> [s,es]

Ram school jata hai - ram goes to school

seema khana banati hai - seema cooks food

वह कर रहा है???

"He Is Doing" --> [ing]

Ram school ja rha hai -  ram is going to school

seema khana bana rahi hai - seema is cooking food/seema is cooking.

वह करता है- he does . ( kar is root verb and you put ta.tee,te in the end of root verb so it become present indefinite sentence )

वह कर रहा है-he is doing.( kar is root verb and ing mean raha hai.)