can somebody tell me the difference?

Stippling is a form of FMQ.

FMQ can be leaves, for example. FMQ just means you are guiding the machine quilting and can change directions as you go.

Stippling is only one form (or pattern) of Free Motion Quilting. Some others are meandering, feathers, pebbles.....

At my class last night, the instructor indicated that in stippling and meandering, the lines of stitching don't ever cross. In FMQ, they do such in as loops and hearts.

stippling is a form of free motion quiting...a stipple is where you stitch an all over design where no line touches or crosses...the difference between stipple and meandering is that fact...stipples your stitches do not touch or cross, meandering can be loops, hearts, stars, flowers...what-ever just meandering across the top.

Here's a ton of designs by Leah Day... just for some ideas on what you else can do wtih FMQ, beyond stippling. :)

http://www.daystyledesigns.com/365project.htm