title: What are .rej files which are created during merge
body: <p>I was merging master branch into new branch, there are some .rej files are created. </p>
  
  <p>I took a pool of master branch into new branch I got conflicts which I've resolved but there are some .rej files.</p>
  
  <p>Can you please help me to know about the .rej files and what am I suppose to do with those files.</p>