Make sure all of the notes in the chord sound clear and your fingers are not touching other strings muting them.
Remember, the Os indicate that string is to be played but not fretted. That is called an Open String when you play it.
The Xs mean to not play that string.
1 - index finger
2 - middle finger
3 - ring finger
4 - pinky finger
The lowercase "m" stands for minor. So, "Em" would be an E minor chord. Whenever there is no "m", the chord is to be Major. So, here we have a G Major Chord and a C Major Chord. The "7" Chord will be explained later, for now just know it as a D7 chord.
Take a close look at the finger positioning for all the chords. The goal is to have as litte hand movement as possible when changing chords. Look at the finger positions for the G major chord. Notice the (1) index finger is on the same fret as the E minor chord. Therefore, when switching between a G and an Em chord you would want to leave your 1st finger planted. There is no need to pick it up.
Next check out the C Major chord, the 2nd finger to be specific. Now make an Em Chord and switch to a C chord while leaving your 2nd finger in the same spot.
Finally to move from a C to D7 chord, your 1st finger stays on the same fret. So you can move through all four of these chords - G, Em, C, D7 - without your hand ever completely lifting off the fretboard. You want to apply this technique whenver possible when changing chords.
A chord progression is a combination of chords played together to make a song. Below is a "50s Style" chord progression example. This chord progression is also called a "Turnaround".
Play the chords below, Strum each chord once and count out loud to four for each.
G Em C D7 / / / / 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4
Now, strum each Chord four times using all down-strokes. Practice slow at first and make sure you get each chord to sound properly.
G Em C D7 / / / / / / / / / / / / / / / / 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4
Play one chord per beat (quarter notes), try to keep time by tapping your foot or counting out loud 1, 2, 3, 4, etc. or use a metronome if you have one.
*A down-stroke means to strum the guitar strings in a downward direction (from the thickest strings to the thinnest).