Basically, the puppet agent will run the catalog it receives from the master, according to his cert name and environment.
this process is know as "node matching".
check out the site.pp in /etc/puppet/manifests (or /etc/puppet/environment//manifests if you are using environments) on you puppet master, to see which manifests your specific node should run.
Also , you can run the puppet agent with the --debug mode:
puppet agent -t --debug
if you are still not sure which manifests are being executed, I suggest adding a notify statement in the begging of each manifest -
notify{'executing module <module-name>':}