A version is like a different "copy" of something. Imagine you draw a picture of a dog on a piece of paper. If you then draw another picture of the same dog but with a slightly different pose, that would be a different version of the dog picture.
When people talk about a version in technology, they usually mean it's a different copy of a piece of software (like an app on your phone) or a file (like a Microsoft Word document). This might happen if the software or file gets updated, or if someone makes a new version with changes to fix problems or add new features.
So, basically, a version is like a new and updated version of something that already exists.