Sensei is sorta complicated to explain. I can understand it well cause it's used about the same way as doctor is in my dialect(not italian). It's more in reference of a status than an actual career.
The best way to explain it would probably be an elevated/honorable position, sorta like when someone has a doctorate but not as high of a requirement.
Senpai, as it's already been said is simply someone above you, usually in years of experience but it can also simply be a higher position in say a company.
Bismarck.Josiahfk said:
»You came back to a thirteen year old asking for Seha's address in another thread.
Hmm...