You are trained in a particular set of Skills favored by thieves and miscreants.

Palm an Object [one-action]

Palming a small, unattended object without being noticed requires you to roll a single Thievery check against the Perception DCs of all creatures who are currently observing you. You take the object whether or not you successfully conceal that you did so. You can typically only Palm Objects of negligible Bulk, though the GM might determine otherwise depending on the situation.

Success The creature does not notice you Palming the Object. 
Failure The creature notices you Palming the Object, and the GM determines the creature’s response.

Steal [one-action]

You try to take a small object from another creature without being noticed. Typically, you can Steal only an object of negligible Bulk, and you automatically fail if the creature who has the object is in combat or on guard.

Attempt a Thievery check to determine if you successfully Steal the object. The DC to Steal is usually the Perception DC of the creature wearing the object. This assumes the object is worn but not closely guarded (like a loosely carried pouch filled with coins, or an object within such a pouch). If the object is in a pocket or similarly protected, you take a –5 penalty to your Thievery check. The GM might increase the DC of your check if the Nature of the object makes it harder to steal (such as a very small item in a large pack, or a sheet of parchment mixed in with other documents).

You might also need to compare your Thievery check result against the Perception DCs of observers other than the person wearing the object. The GM may increase the Perception DCs of these observers if they’re distracted.

Success You steal the item without the bearer noticing, or an observer doesn’t see you take or attempt to take the item.
Failure The item’s bearer notices your attempt before you can take the object, or an observer sees you take or attempt to take the item. The GM determines the response of any creature that notices your theft.

Thievery Trained Actions

Disable a Device [two-actions]

This action allows you to Disarm a trap or another Complex device. Often, a device requires numerous successes before becoming disabled, depending on its construction and complexity. Thieves’ tools are helpful and sometimes even required to Disable a Device, as determined by the GM, and sometimes a device requires a higher Proficiency rank in Thievery to disable it.

Your Thievery check result determines how much progress you make.

Critical Success You disable the device, or you achieve two successes toward disabling a Complex device. You leave no trace of your tampering, and you can rearm the device later, if that type of device can be rearmed.
Success You disable the device, or you achieve one success toward disabling a Complex device.
Critical Failure You trigger the device.

Pick a Lock [two-actions]

Opening a lock without a key is very similar to Disabling a Device, but the DC of the check is determined by the complexity and construction of the lock you are attempting to pick. Locks of higher qualities might require multiple successes to unlock, since otherwise even an unskilled burglar could easily crack the lock by attempting the check until they rolled a natural 20. If you lack the proper tools, the GM might let you used improvised picks, which are treated as shoddy tools, depending on the specifics of the lock. 

Critical Success You unlock the lock, or you achieve two successes toward opening a Complex lock. You leave no trace of your tampering.
Success You open the lock, or you achieve one success toward opening a Complex lock.
Critical Failure You break your tools. Fixing them requires using Crafting to Repair them or else swapping in Replacement Picks (costing 3 sp, or 3 gp for infiltrator thieves’ tools).