This is one of the first topics any programmer would need to know. Every company would want their employees to know about Git. They say one understands a topic perfectly if you can explain it to a kid! Let me try.
When a student has to complete his summer project, he has many components to complete - cover pages, content, decoration, and finally cribbing about the project and making their parents do it for them. Anything he does in his project won't magically affect his friend's project, they just aren't inter-connected.
But, when you get to the higher classes, your projects go from individual to groups. You aren't the only one doing all the work (hopefully). You divide your share of the work, check if everyone has completed their share, make sure that there are no contracting statements in anyone's part and make your complete project look neat and clean! How would you manage so many things with your friends normally? You might WhatsApp them about the changes or maybe email them.
When a programmer codes for a project, he also has similar needs to collaborate. For this, we don't use WhatsApp, instead, we use Git.
In the professional programming world, working with your colleagues requires each of you to save your code, merge it with the project, retrieve any previous saves etc. This is all done by Git! GIT was developed by Linus Torvalds in 2005. It helps developers keep track of their code and the changes in the code and also allows collaboration on a common codebase.
Now, Git doesn't just save a new file of code everytime you use it, it doesn't keep track of every single line of code, it keeps track of every change in line of code since it was last laved. Git is a way for you to check how far you have come since you last saved your code. That's little dramatic but it's alright!