This Incoterm is not often used nowadays. It means that the seller has the responsibility of delivering the cargo "alongside the ship". While this is workable for break-bulk cargo, for containerized cargo it doesn't work as well. Containers are delivered at a terminal, and not alongside a ship. For containers delivered at terminal it is better to use the Incoterm FCA, specifying the collection point as "port terminal", or FOB - Free on Board.