Capture level determines number of objects you can capture. You can capture a large number of things, including all magic circles, and most traps. Here are SOME notable/interesting examples (there are many, many, more).
• Broom Trap (Sapper)
• Magic Arrow (Fletcher)
• Chortasmata (Druid)
• Circling (Falconer)
• Raise (Psychokino)
• Cure (Cleric)
• Heal (Cleric: The entire set of Heal counts as 1)
• Lachrymator (Rogue)
You can only use Capture on enemy or allied magic circles. Neutral magic circles, such as ones from other parties or un-partied players, cannot be captured.
Re-deploying Capture places all captured magic circles directly in front of you. Any magic circle you capture benefits from YOUR stats and acts as if it were the rank level of the person who deployed them. They will also take all of your passives into account, for example deploying a Cure with a bow equipped will allow Cure to deal double damage on flying [boss] enemies.