Even though the term open source is becoming commonplace for knowledge, guidelines or even products, one usually refers to software when using this term.

A software for which the original source code is made freely available and may be redistributed and modified according to the requirement of the user. Open source software is that by which the source code or the base code is usually available for modification or enhancement by anyone for reusability and accessibility. Open source code is the part of software that mostly users don't ever see. Anyone can manipulate and change a piece of software so that the program or application can work. Programmers who have access to a computer program source code can improve a program by adding features to it or fixing parts that don't always work correctly. https://economictimes.indiatimes.com/definition/open-source