What is open source? According to ‘Mass Communication In Canada’ book. Open source software is the production and development of software that allows users and others to see source code and thereby make adjustments to it to suit their needs.
In other words, open source is a source code available to the general public for use and modification from its original design free of charge for any purpose. It’s free for modification, use, and distribution.
There are many examples of open source software I can say most of the popular open source software for users is Firefox