In the first position, the chord is written x0201(0/3), while the notes are written x - A - E -G - C - (E/G). In the 2nd position alternate (alt) chord, the chord is written 57(5/7)585, while the notes are written A - E - (G/A) - C - G - A. Both these chords simply take into account the optional note, which is the number/letter after the forward slash (/). You don't have to play these optional notes, but once you become more competent as a player, you may want to try them.
When you are learning guitar, you will find this chord one of the easiest to play. It is often used in conjunction with the Am chord.
Standard keys using the Am chord: C Major, G Major, F Major, Am, Em, and Dm. Each of the minor keys is a relative minor of the major keys, i.e., C/Am, G/Em, F/Dm. If you are playing songs in any of these keys, you will more than likely come across an Am or Am7 chord.
If you want to practice playing a song with Am7 chords, you could try Bruno Mars - Count On Me. It uses an Am7/G chord which simply means Am7 leading with a G bass note, but you don't have to play the bass note if you don't want to as the Am7 chord has a G note in its chord structure.