They are two different things. ISO17025 is a compliance standard document. A2LA is an organization that performs accreditations. A2LA is one of the organizations that performs accreditations to ISO17025. If you go to www.a2la.org, you can see details of what they do. You can go to an ISO or one of numerous other websites to get a copy of ISO17025.
Thanks, Jerry. I had a potential supplier mention that they were A2LA accredited in a context where I thought it was a standard I was unfamiliar with. No wonder I couldn't find a thread that discussed it in that manner.