title: In Azure DevOps or Team City what is a build agent?
body: <p>I'm fresh in the area of CD/CI and I need to implement it in an old project from my company. From what I have read we have a couple of options like Azure DevOps or Team City, I chose these two options because most of our projects are built in Microsoft technologies.</p>
  <p>I have been reading for a while, but I cannot grasp the proper definition of a <strong>Build Agent</strong>; also, I found this old question, but the answer is <em>unclear</em>:</p>
  <p><a href="https://stackoverflow.com/questions/3891530/in-team-foundation-server-what-is-build-agent-and-controller">In Team foundation server what is build agent and controller?</a></p>
  <p>Further, I read different documentation:</p>
  <ul>
  <li><a href="https://docs.microsoft.com/en-us/azure/devops/pipelines/agents/agents?view=azure-devops" rel="nofollow noreferrer">Azure Pipelines agents</a></li>
  <li><a href="https://www.jetbrains.com/help/teamcity/build-agent.html" rel="nofollow noreferrer">Build Agent</a></li>
  </ul>
  <p>And their definitions are the following ones:</p>
  <blockquote>
  <p>An agent is installable software that runs one job at a time.
  <strong>Microsoft</strong></p>
  <p>A TeamCity Build Agent is a piece of software that listens for the
  commands from the TeamCity server and starts the actual build
  processes. <strong>JetBrains</strong></p>
  </blockquote>
  <p>However, I cannot understand exactly their role or purpose, do they build the <em><strong>Test</strong></em>, <em><strong>UAT</strong></em> and <em><strong>Production</strong></em> pipelines in parallel to see if the compilations were successful? Like here:</p>
  <p><a href="https://i.stack.imgur.com/cbU8o.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cbU8o.png" alt="preview" /></a></p>
  <p>Or what do they do? Since the solution has multiple projects inside maybe 8 or 10.</p>
  <p>You can take the example that I gave in the comments below:</p>
  <blockquote>
  <p>Let's 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. What would represent these agents?</p>
  </blockquote>
  <p>Thanks for any explanation.</p>