The GPL (General Public License) is one of GNU’s most popular open-source licenses. Richard Stallman created the to safeguard the GNU’s software from being proprietary. It’s a great implementation of his concept referred to as “copyleft.”
If you’ve used any component of a GPL in your software, then the whole software is considered the ‘work based on the GPL. As such, you aren’t allowed to claim copyright or patent on the software. Furthermore, you’re obligated to display a warranty disclaimer, copyright notice, copy of the GPL, and intact GPL notices.