边 (traditional 邊) carries the walking radical 辶 — the edge or border is the limit you reach when you walk to the far side of a place. It means side, edge, border, margin.
边 turns directions and positions into 'sides': 上边 (the top), 下边 (below), 里边 (inside), 外边 (outside), 东边 (the east side), 这边 (this way/side), 那边 (that way). Doubled as 一边…一边… it means 'doing two things at once': 一边吃一边看 (eat while watching). It's one of the most flexible location words you'll use.
Walk (辶) to the limit of a place — its SIDE, its EDGE.
一边…一边… means 'doing two things at once': 一边走一边说 = talking while walking. Add 边 to any direction (上边, 外边, 那边) to make it a 'side'.