I am learning to play guitar and, in some videos I have seen in youtube, people play a song in the background (that has muted the guitar part) so they play it themselves. Is there a software to do this?
No, you need the original stems. Guitarbackingtrack.com has been the most comprehensive collection of free backing tracks for guitarists for many years, I'm sure there are other similar sites too. Back in the day these were mostly fairly awful midi based backing tracks, but these days that's often no longer the case.
Since guitar hero/rock band came out, a lot of the stems of original recordings have surfaced, so often people use them to make guitar backing tracks, by recombining the stems but leaving out the guitar part. This has been a huge boon for the quality of freely available online backing tracks, as before this all backing tracks were laid down from scratch (usually by hobbyists)
compare side by side
what it used to be like when I started: https://www.guitarbackingtrack.com/play/jimi_hendrix/foxy_lady.htm
what newbies today are blessed with ;) https://www.guitarbackingtrack.com/play/jimi_hendrix/foxy_lady_(2).htm
There are a couple of things that many people would LOVE their computer to be able to do. One is to take a recording and convert it into musical notation (and vice versa). The other is to extract single instruments from a stereo mix. Actually, they're both aspects of the same basic need.
I hesitate to say we will NEVER be able to 'un-bake the cake' into its individual ingredients. Computers are very good at analysis, and you bet the military are very interested in being able to isolate single voices from a babble. When they perfect that, we'll likely get a spin-off. But it's not here yet.
There is 'vocal removal' software. IF a stereo recording has the vocal (and nothing else) panned dead center, it can sometimes considerably decrease it. But a karaoke track is not made this way, from processing the original recording, not for copyright reasons but because it doesn't work very well!
I've always use Guitar pro, which provide detailed tabs for every instruments. This software allows you to mute/isolate any instrument. Although it's MIDI sound, it's still really useful to help you practice.
You can find pretty much all tabs on https://www.ultimate-guitar.com/, they're made by the community but they're usually pretty good.