I have a mass on left side of neck and a mass on left under arm pit. can you please tell me what this is?

Neck and Axilla mass: Likely these are lymph nodes. I recommend expert exam. Their enlargements could be worrisome.

Need biopsy: There's no way to tell what it is by your description above. Any symptoms? Have you been losing weight? Do you have night sweats? Have you had any abnormal mammogram? The only way to be sure is to undergo a biopsy of the mass & have a Pathologist look at it under a microscope. They may need some imaging tests to figure out the best approach beforehand. Beyond that, all is speculation. Best of luck