In Azure DevOps or Team City what is a build agent

Question

I need to implement CD/CI in an old project from my company. I have two options in my mind to proceed with this and they are Azure DevOps or Team City. I wish to know the proper definition of a Build Agent. I haven't exactly gotten the role or purpose of it, do they build the Test, UAT, and Production pipelines in parallel to see if the compilations were successful?

 Like here:

Or what do they do actually?

Answer 1

Build Agent is like a computer process that has many capabilities to perform a build. Some agents can perform certain jobs, while other agents are more general purpose. Sometimes a computer can have multiple agents that can work in parallel. Agents can be "local" which means they are on the server where they build software and they can also be "remote" or on a different computer.
Suppose you create a project in Azure DevOps for your new CRM for a Dentist with a Debug, UAT, and Release environments plus a team of 5 devs. You only need agents. The agent would build and then deploy to the different environments. The agent would be the computer process that Azure allocates for building and then deploying.