step dancing vs dancing

step dancing and dancing both are nouns.

Word	Noun	Adjective	Verb	Adverb
step dancing	Yes	No	No	No
dancing	Yes	No	No	No

As nouns, dancing is a hypernym of step dancing; that is, dancing is a word with a broader meaning than step dancing:

step dancing: dancing in which the steps are more important than gestures or postures
dancing: taking a series of rhythmical steps (and movements) in time to music

Other hypernyms of step dancing include dance, saltation, terpsichore.

step dancing (noun)	dancing (noun)
dancing in which the steps are more important than gestures or postures	taking a series of rhythmical steps (and movements) in time to music