Hi Amber,
The infections listed in your screenshot [PUP] are Pups, which stands for "Potentially Unwanted Program"
As a rule, these are not "infections" in the true sense of the word, but based on many user votes, programs that do things that may be generally considered annoying, like initiating popup or links to sites to promote (spam) purchasing of other software.
For my own part, anything that Avast indicates as a PUP (on my PC - I'm a relatively new MAC user myself) I get rid of. But that's my own personal choice of action. You can follow Avast's recommendation and allow it to remove those programs (this is the recommended action by me) or simply tell it to ignore them if they're not causing you any grief.
Hope you found this information helpful.
Regards,
Andrew