closed software is the opposite of open source. unlike opensource, closed sources software is when the source code in not available, meaning you can make changes. since you can't see the source code, you cant see what are the intention of the company who developed the software. an example of closed source software is microsoft windows.

if you are not a programmer, then you really wouldnt care if the software application or programm you are using is closed. but you should beware of software with spyware.