Fine needle aspiration biopsy

Hi there, I'm totally new here, but am really worried and not sure where to turn. 

I found a lump in my neck a few weeks ago and went to see my GP about it. He referred me for a blood test which came back inconclusive. He said he'd then refer my for a scan. 

I've just had a letter today to say I've got an appointment in a few weeks for a scan and FNA. The doctor didn't say anything about having to have one of these. 

Was hoping someone could help me through what the process of this is, and what it's purpose is. 

I daren't look on Dr Google as I'm sure it's full of horror, so thought I'd ask here first. 

Thanks in advance