Reading chords within guitar tab is a relatively simple process. When a tab displays a series of numbers, stacked vertically, it is indicating to play all these notes at the same time.
The above tablature indicates that you should hold down the notes in an E major chord
(second fret on fifth string, second fret on fourth string, first fret on third string) and strum all six strings at once. Often, tablature will also include the chord name (in this case E major) above the tablature staff, to help guitarists recognize the chord more quickly.