Open Source Browsers
Short version - Firefox is an Open Source Browser.
Open source usually refers to programs that a user can easily get the source code for. The idea is to be able to make changes to meet the user's needs or to update the program as standards change.
The meaning that most people place on open source is that it is a program that is available free.
Many open source programs are available in a variety of languages and are able to run on a variety of oiperating syustems.
Browasers are the programs that enable your omputer to interact with the internet.
So, an Open Source Browser is a free program that lets your computer interface with the internet.