Learn French: Ils attendent une lettre de mon frère. - They are waiting for a letter from my brother.

In French, the verb attendre means "to wait for" all by itself. You don't need to add an extra word like pour. You just put the thing you are waiting for directly after the verb, like attendre une lettre (to wait for a letter).

How is the -ent ending on attendent pronounced?

It isn't! For regular -re verbs, the -ent ending for ils and elles (they) is completely silent. You just pronounce the base of the verb, which sounds like "ah-tahnd".

Should I connect the words Ils and attendent when speaking?

Yes. Because Ils ends in an 's' and attendent starts with a vowel, you make a liaison. This means the normally silent 's' is pronounced as a "z" sound that connects the two words: "eel-zah-tahnd".

Why is it mon frère instead of ma frère?

Possessive adjectives like "my" have to match the gender of the noun they describe. Because frère (brother) is a masculine noun, you must use the masculine form mon. You would use ma for feminine nouns, like ma sœur (my sister).