piano chord
Em6
E1G♭3B5C♯6
A minor triad with a major sixth added, which is why it is not simply a minor chord with a flat seventh.
What is true of it
Em6 is E, G, B and C♯ — 1, b3, 5 and 6 counted from E.
These are also the notes of C♯m7♭5/E and D♭m7♭5/E. Which name is right depends on what is underneath and what came before — the notes alone do not decide.
On an instrument that cannot reach all 4, the 5 goes first, in that order.