If you are captured during combat, or siege, you must pay a ransom. If you are captured in combat or duel the alternative is death. At tourneys you can welch on your ransom, but then the noble you stiffed can challenge you to a duel to the death. Ransoms are fixed as a percentage of your GDP at the time of capture. This concept is called "auto-ransom." If you pay right away, you are automatically released and may move up to 10 fiefs in any direction you choose, but you have no days left in that season for moving. You can't travel, or do much of anything else except manage your fiefs while a prisoner. You can attend the IC. Any player may also attempt to negotiate a lower ransom than the one the game sets.