Why do we need to build a pull request when we are already building every commit from source branch

[chakilams]

Hi everyone,

Im new to this "pull request" world , and I am looking to configure "Bitbucket pull request builder plugin", but before I start using this , there is a question that is bugging me a lot.

Using a post webHook, We have configured our Jenkins server to automatically detect any commit pushed to any bitbucket branch and start building.

But my basic question is "Is there a fundamental difference between building commits individually vs building a pull request" ( end of the day pull request is just a bunch of commits which are already build by Jenkins.