I have browsing job offers for developers and a lot of those offers ask you to know/be/do Agile. Searching online provides a few articles that give a good idea of what is Agile and how to use it in software development.
I get the idea behind Agile and Scrum, it's a great way to manage a project, delivering incremental features within a certain time. It helps you become more productive and keep your projects tidy because you know exactly what to work on next.
The post The Beginner’s Guide To Scrum And Agile Project Management gives a good insight into Agile and the Scrum framework and how to implement it with Trello. But it assumes you are working as a team.
If you are working alone, how about the need to have a Product Owner and a Scrum Master, surely you can do all of it if the project is managed by you, but then the challenge lies in keeping yourself accountable which can somewhat destroy the whole method if you don't have enough discipline.
In essence, my question about Agile and Scrum is that if you are a self-taught developer, can you claim to know Agile if you follow the methods and the Scrum framework, but don't have any formal training/certification?