Verbals are infinitives (to sleep, to dream) and -ing verb forms (sleeping, dreaming) that may look like verbs but are actually functioning as nouns or modifiers.

If you correct a fragment by attaching it to the previous or next sentence, make sure you haven’t just turned it into a dangling modifier:

Prancing back and forth onstage, the audience couldn’t take their eyes off Gordie.

The audience couldn’t take their eyes off Gordie prancing back and forth onstage.