Scrum unlike the Agile principles is a practical framework with clear rules on how it can be implemented. Scrum gained popularity after the millennium. Scrum is defined as a framework within which people can address complex adaptive problems, while productively and creatively delivering products of the highest possible value. Per the Scrum guide, Scrum is a framework that has been used to manage complex product development since the early 1990s. Scrum makes clear the relative efficacy of your product management and development practices so that you can improve. There is no doubt that Scrum has become the mainstream Agile methodology in the IT industry. With the growing popularity of Scrum and Agile, it has become easier than ever to find free resources to learn it theoretically.
Here is a list of learning resources to learn about agile methodology & scrum methodology:
1. Scrum Guide [PDF]
2. Agile Manifesto
3. Scrum Alliance
4. Agile Alliance
5. Scrum.org
6. Mountain Goat Software
7. Trello and ReQtest
8. Scrum or Agile Google Groups
9. Scrum Meetup Events
10. ScrumHub
11. Scaled Agile Framework
12. Stack Overflow
13. Wikipedia
14. Collabnet
15. ReQtest Blog
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath