French language Q&A Forum

I don't understand what the difference is exactly between nous and on

For example: Je nettoie la vitre de la voiture - J'en nettoie la vitre

1) To copy (record) something onto a notebook : copier qch. dans un carnet ?

2) To copy (fraudulently) the exercise from a friend : copier l'exercice sur un ami ?

3)  To copy some sentences from a book  : copier des phrases sur un livre ?

 "alors il va préparer l'entré", aint it should be "elle" not "il" referring to her mom ?

This is perhaps a bit off topic since it isn't about the French grammar point at hand, but the tip regarding the English construction is inaccurate. It says "Whereas in English, you will need to use a subject pronoun after than (... than I (do), you (do), he/she (does)...)". I know there are people who think this is a real rule, but it isn't how anyone actually speaks, and many dictionaries (e.g. Meriam-Webster's) acknowledge the use of object pronouns here.

Ce n' est pas le saint esprit qui est parti mais LES DISCIPLES donc qu'ils partent. 

The pronunciation I'm hearing in the audio sounds like ". . . ce que t'way le voir" for " . . . ce que tu ailles le voir."

Is this actual French pronunciation or a bad recording? 

I'm wondering if one would say "Je l'ai appelé(e?)." or "Je les ai appelé(e?)s." I've seen entries giving it as a feminine singular noun (based on 'la police' perhaps?), masculine singular (based on 'le secours' I'm guessing...), and plural. If it can be either or if it's "none of the above", I would like to know. Merci.