The wasla

The wasla? What's the wasla? I had no idea, until Wendy used this word in class, that there was a specific name for the slurring of the wa (and) into the following word. Okay, so wasla makes sense.

And the dammatein, fathatein, kasratein, all the specific use of the short vowels in the tanwin to create cases in the indefinite. -An, -on-, -in.