disabled - trade disabled by admin (till manual activation).
delayed - trade disabled by script, and will be activated according network's 'Additional settings: Speed of trades addition'. Trade can be activated by admin at any time also.
blocked - when you adding new trade, you have the option:
Send a message to site owner about this trade.
Email above must be setted. Trade status will be setted as 'Blocked'. Since admin confirm the link in the email, trade status becomes 'Active'.