버리다 is throwing something away, and five of the eight lines use the standard phrase 갖다 버리다 — take the thing somewhere and get rid of it (갖다 버리면 다시 와 있고, I throw it away and it's back again). 내다 버리다 is the same idea with a stronger sense of chucking out, and 씹다 버린 껌 is gum chewed and then discarded. Note 버리다 also works as a helper verb meaning 'and that was that', a separate use from this one.