meld is a graphical software tool that allows the user to compare and merge the differences between files and folders.
It is commonly used when resolving merge conflicts between two files with are under a version control system such as git.
Compare Two Files
The simplest way to run meld is to compare two files with:
$ meld file1.c file2.c
This will open up the two files in a graphical interface, where you can easily see the differences and merge if required.