NTFSresize is like a magic tool that can help resize or change the size of the space on your computer where your files and documents are stored. It's kind of like when you're playing with legos, and you have a big block for your tower, but you want to make it a little smaller or bigger to fit more legos.
Basically, your computer has a special place called the "hard drive" where all your files and documents are saved. NTFSresize helps you change the size of this hard drive space so you can have more or less room to store your stuff.
It's really useful because sometimes you may need more space to download a game or movie, or maybe you want to clean up some old files you don't need anymore to free up space. NTFSresize makes it easier to do this.
Just like how you carefully take apart and put together your legos, you have to be careful when using NTFSresize because if you mess up, you can lose all your files and documents! That's why it's usually a good idea to ask a grown-up or a computer expert to help you if you want to use NTFSresize.