There are two ways we can start Jenkins Node agent :
We can start a Node agent from a browser window itself.
There is another way of starting an agent from the command line as well.
The JNLP file gets downloaded when we start an agent using a browser window.
When this file runs it triggers a separate process to launch Jenkins jobs. There is a different process which runs in case of agent get launched from the command line.
There is one JAR file which is required on the client machine and this file gets launched from the command line but still, you need to refer slave agent JNLP file available on Jenkin server.
The command line triggers a process on the client machine which actually communicates with Jenkin’s mater and triggers build jobs in Jenkin when it identifies idle clock cycles