You have captured a ship and are preparing to plunder it. If you lost cannons in the fight, excess cannons will have been transferred from the captured ship to replace those you lost. You now have to decide which goods from the captured ship to take and which to leave behind. You can also choose to dump goods currently on your own ship.
The Status button allows you to view the status of your own ship. The Cargo button will take you to the cargo view, where you can take goods from the captured ship into your own ship. The Seize button allows you to perform a cursory repair of the enemy ship and take over command of it for yourself. This will replace your current ship with the enemy ship.
Sometimes, the captured ship may be carrying some particularly skilled crew members. If these are present (and you do not already have a crew member with the same skill), you will be given the option to try and recruit them.