Open source software refers to software with source code that anyone can access, modify, and share. Examples include Linux, Firefox, and OpenOffice. Proprietary software source code is owned by its creator, and users cannot modify or share it without permission. Open source software is free to use and modify, has better security due to many reviewers, and faster fixes. However, it offers less support and increases business risk. Proprietary software has usability, stability, and tailored support, but users are dependent on the company and cannot verify what the software actually does without the source code. Overall, both approaches have pros and cons depending on the situation and needs.