Closed source software (also known as proprietary software), the public is not given access to the source code, so they can’t see or modify it in any way.
Examples: Microsoft Windows, Apple macOS

While open source software is a source code that is publicly available to anyone who wants it, and programmers can read or change that code if they desire.
Examples: Linux, Android

Source:
https://edu.gcfglobal.org/en/basic-computer-skills/open-source-vs-closed-source-software/1/