elementary; basic; rudimentary
Describes something at the very beginning level, often implying it is too simple or lacking sophistication.
His question was too elementary, so nobody answered.
I made a basic mistake.
初級 is a noun meaning 'beginner level', often used for classes or materials, whereas 初歩的 is an adjective describing the nature of something as elementary.
Compound of 初歩 (shoho, 'first steps, basics') + 的 (-teki, '-like, -al').