沿着 is a preposition-like verb phrase meaning 'along (a path, route, or line)'. It indicates that an action follows a continuous line or direction. You can use it with physical routes (roads, rivers) or figurative lines (a coastline, a corridor). The word is formed by 沿 ('along') plus 着 (the durative aspect particle), but it's treated as a fixed unit. The structure is: 沿着 + [noun of path/line] + [verb of movement/arrangement].