I like what Vine's Dictionary says about it:
2Strong's Number: g1984Greek: episkope
Bishop (Overseer):
besides its meaning, "visitation," e.g., 1Pe 2:12 (cp. the Sept. of Exd 3:16; Isa 10:3; Jer 10:15), is rendered "office," in Act 1:20, RV (AV, "bishoprick"); in 1Ti 3:1, "the office of a...