Edim7 (E diminished seventh) is a four-note chord made from E, G, Bb and Db. A diminished seventh is minor thirds stacked all the way up, so it is symmetrical: the same shape moved up three frets plays the same notes. It makes a tense passing chord that leads up a half step.
Built from the root E, the minor third G, the flat fifth Bb and the diminished seventh Db.
Frets from low E to high E; x means don't play that string.
Easiest shape to start with: Open position (012020). It has 3 open strings and nothing above fret 2.
Every note of Edim7 is in these keys. The numeral is its place in the key.