Lymph nodes and cysts?

ok im having alot of medical problems at the moment which is in another post of mine if you care to look at them, but my question is specific to lymph nodes and cysts i had a CT scan done of my lower abdomen and for the most part they didnt find anything out of the ordinary except..."a small incidental less then 1 cm cyst noted of the superior pole of theleft kidney" and ..." nonspecific scatted subcentimeter lymph nodes noted in the right lower abdomen of questionable clinical significance" (which i have to return to the docs in about 4 months to have a follow up CT scan because of) ...ok so my question is wtf are the lymph nodes? what exactly does that mean? arent lymph nodes located all throughout the body? why would they be of possible clinical significance? and also what exactly is a cyst and why isnt that clinically significant at all? ...any info is more than welcome, thank you =)