I am Software Engineer with a testing background and I will explain:

1) Developers how to write cleaner and more testable code. TDD, Clean Code, XP, Agile, these sorts of things.

2) SDET and TA Engineers - how to create efficient automated testing. Test automation, test strategy, DevOps.

3) Junior developers - the fundamentals they need to know to build a successful career. Data Structures and Algorithms, career progression and interviewing tips.