The French expression pas mal (pronounced "pah-mahl") is a handy phrase to know because you can use it in a variety of ways in casual conversation. Literally translated, it means "not bad" in English and can be used to respond to common questions such as ça va? or comment allez-vous? But pas mal can also be used as an exclamation of approval, along the lines of "nice job, way to go!"
There's also another, completely different way to use pas mal: in reference to a "fair amount/number" or "quite a bit" of something. It can be used with nouns, in which case it must be followed by de, as well as with verbs. Note that there is no ne to go with the pas and that de follows the rules of other adverbs of quantity, meaning that even in front of plural nouns it's usually de not des.
- Tu l'as fait en dix minutes? Pas mal! > You did it in 10 minutes? Not bad / Way to go!
- Il gagne pas mal d'argent. > He earns quite a bit of money.
- J'ai pas mal de questions. > I have quite a few / a fair number of questions.
- Nous avons discuté pas mal d'idées. > We discussed quite a few ideas.
- Elle a pas mal voyagé. > She has traveled quite a bit.
- Vous allez voir pas mal là-bas. > You're going to see quite a bit over there.