E/G♯ means “E with G♯ in the bass”: play a E major chord and make G♯ the lowest note. Because G♯ is already in the chord (its major third), this is the first inversion of E.
The notes, low to high, are G♯, E, B. The library above opens on E/G♯ with 14 shapes that keep G♯ at the bottom; tap one to hear it.