Basic music theory is extremely important to help you do many things such as:
- Write your own songs
- Figure out what chords are in a song
- Figure out what scales to use in a song
- Jam with other musicians
This lesson here on the tempomusicards.com website will explain in simple terms how to figure out the chords in any key. Included in the lesson are a few simple exercises that you can try out to practice figuring out the chords.
Check out the lesson here.