后 (also written 後) is the mirror of 前. It means behind in space and after in time. Curiously, 后 also once meant 'sovereign / queen' (皇后 = empress) — a ruler stands behind and above. Modern simplified Chinese merged both into 后.
后 pairs everywhere with 前: 后面 (behind), 以后 (after/later), 后天 (the day after tomorrow — with 天). 然后 (then/after that) strings events together. And 皇后 (empress) keeps the old 'sovereign' sense. If 前 is the past you can see, 后 is what comes next, at your back.
The opposite of 前 — BEHIND, AFTER.
后 also means 'empress' (皇后) — a queen who stands behind the emperor. Simplified Chinese folded the old 'sovereign' character into the everyday 'behind/after' one.