Could you explain the use of 'pendant que' in this sentence.

Question

Nous avons attendu pendant qu'il changeait le pneu.  Why is 'que' needed? The 2nd clause uses the imparfait. So, except for le present, can other tenses follow 'pendant que' ?

Accepted Answer

The expression is “ Pendant que”  (or tandis que) - while, as a conjunction. “We waited while he was changing the tyre”.  Apart from the need for an expression for ‘while’, this is similar to English.  English can of course also use ‘changed’ instead of “was changing”, whereas French uses the imparfait in the 2nd clause.
 https://www.wordreference.com/enfr/while

Answer

You need "que" in addition to "pendant" because the two clauses have different subjects:

Nous avons attendu pendant qu'il changeait le pneu. -- We waited while he was changing the tire.

This rule works for all conjunctions that can be used with our without "que". For example "avant":

Tu finiras tes devoirs avant que maman ne revienne. -- You'll finish your homework before mom returns. Here, again, are two different subjects ("tu" and "maman") and therefore also "avant que".

Je finirai mes devoirs avant de sortir. -- I'll finish my homework before going out. There's only one subject for both clauses ("je") and therefore also no "que".