JH'sH: Thanks for the chords -- that's perfect! Okay, I can see that you're playing the song in the key of G. Therefore, the G chord is your "I" (Roman numeral One) chord.

The C chord is named thus because C is the note that's the root of the chord. The note C is four whole notes up the scale from the note G (or, if you were singing it as "do re mi fa", G would be "do" and C would be "fa"). Therefore, the C chord is your "IV" (Roman numeral 4) chord.

The D chord: D is the note that's the root of the chord. The note D is five whole notes up the scale from the note G (if sung as "do re mi fa so", G would be "do" and D would be "so"). Therefore, the D chord is your "V" (Roman numeral 5) chord.

What about the Em chord, you ask? ...You did ask, didn't you?... That's the "VI" (Roman numeral 6) chord, because E is six whole notes up the scale from G ("do re mi fa so la"). It's a minor chord because it is a -- deep breath here as I introduce a new phrase -- "scale tone chord". The chord (E-G-B) is made up of three tones (the "la", "do" and "mi" notes) that appear in the G scale (G-A-B-C-D-E-F#-G), so it comes out as a minor chord in the G major scale.

Now, here's why we've got this fancy-schmancy Roman numeral system in the first place: The system makes it easy to figure out the chords when you change keys. Pretend that you found the "Flowers" song really hard to sing in the key of G and you wanted to sing it in a key that would be more comfortable for your voice instead, like D. So that would make the D chord your "I" chord. The D scale is D-E-F#-G-A-B-C#-D. So what's your "IV" chord? G. Your "V" chord? A. Your "VI" chord? B minor.

All of this might sound confusing and perhaps even somewhat useless to you at the moment, but trust us when we tell you that it's worth learning. Since so many songs are written in a I-IV-V format (not always with that VI thrown in!), you should practice playing those chord changes in different keys so your chording hand will get used to switching back and forth among them. Here's a chart that shows you the I-IV-V chords in every key: I-IV-V chord progressions

Here's a page that discusses the Scale Tone Chords in more detail: Scale Tone Chords

Here's more stuff about chord progressions, including II-V-I and III-VI-II-V-I: Chord Progressions explained

Here's a page with a piano keyboard display, which will show you the notes that make up different chords when you click on the chord name: Chords and Scales on Piano Click the "play" button to hear the notes in a chord. This will help you to learn the notes you should be hearing when you play the chord on guitar.