meaning of 'folk songs' and 'rhythm'

[Learning_English]

They were always the first couple on the floor to dance, and the first to start singing the old folk songs while the rest of us clapped hands to the rhythm.

Please tell me the meaning of `folk songs' and `rhythm' in this sentence.
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Please let me know if I have made any mistakes in any of my sentences.

[Conchita]

Folksongs are traditional songs and rhythm is a regular beat in music, poetry, etc.