Hi!
What you're looking at are chords, which are two or more notes struck simultaneously. Each chord is based on one of the notes in the chord, usually the lowest. So for Example, F# would consist of an F#, A#, and C#.
Sometimes, a chord will have a different kind of sound. That is usually noted after the letter. For example, your D#m is a D sharp minor chord. The D# is just as I noted above for the F#. It's the lowest note in the chord. The m tells us it is a minor chord. Minor chords have a more somber, mellow tone.
It's also worth noting that every chord is derived from some scale, usually (but not always) indicated by the chord name. For example, your F# chord is derived from the F# major scale. Your D#m is derived from the D# minor scale (which is itself derived from F# major).
You can use this chord chart to help you learn chords.
http://www.chordie.com/chords.php
If you're just starting out, learn the following
C A G E D
If you can move easily between those five chords, you'll be able to play thousands and thousands of songs.
This is a good place to learn about this stuff. But all of it boils down to learning scales. So buy yourself a book, and practice, practice, practice.