1-means "for", but it refers to an action in its entirety that has no relation to the present. It can be used for both the past and the future.
ex:
Pendant combien de temps avez-vous étudié le français ?
How long did you study French?
J'ai étudié le français pendant 3 ans.
I studied French for 3 years.
Je vais habiter en France pendant 2 mois.
I'm going to live in France for 2 months.
2-also means "during".
J'ai vu un film pendant mon séjour.
I saw a film during my stay.
Pendant ce temps, il m'attendait.
During this time, he waited for me.