What is SHA Algorithm or Hashing? Is this concept only in Crypto World?

Well, the answer is no.
SHA Algorithm or can be said function is just a tool , and one use case is in Crypto World.
SHA , which stands for Secure Hashing Algo. is a function which emits fixed length of Hex codes for any word, lines of codes or installer files or whatever you insert into the function.
In Crypto-World, SHA is emitted out for every successful transaction being added to blockchain. and if it is 256 ... length, we call it SHA-256 Algo. SHA since being a unique number is a unique log for particular transaction.
Now, SHA can be useful even when you are downloading software.
Imagine you have to download Ubuntu Software.
1st option is: you can download it from single source server of Ubuntu website.
2nd option is: If you think I would download it from torrent (where you can download it from multiple peers simultaneously in chunks) , then you may end up downloading Ubuntu from some source (or say hackers) who have inserted malicious codes in to it. Now since SHA is a unique number generated for some lines of code (in this case, software as a whole), then even adding a single bit to the whole Ubuntu software alters its SHA number.
Think of it this way:
If I insert my name cryptonauthop to SHA generator, it creates one SHA.
Now, even if I alter my name just by cryptonaut-hop, SHA would be different.
So, to make sure that I download exact Ubuntu Software where not even a line was added or minuend, I simply copy its SHA number from official Ubuntu and then torrent Ubuntu only from peers which has got same SHA Ubuntu.

Now, you understand it when you see the SHA number in different versions of code in Github, don't you?