This term means that the seller delivers when the goods are placed alongside the vessel at the named port of shipment. The seller is required to clear the goods for export. The buyer has to bear all costs & risks of loss or damage
to the goods from that moment. This term can be used for sea transport only[1]

“Free Alongside Ship” means that the seller delivers when the goods are placed alongside the vessel (e.g., on a quay or a barge) nominated by the buyer at the named port of shipment. The risk of loss of or damage to the goods passes when the goods are alongside the ship, and the buyer bears all costs from that moment onwards.[2]

Reference

[1]

[2] https://iccwbo.org/resources-for-business/incoterms-rules/incoterms-rules-2010/