A Lasting Power of Attorney is arranged by you while you still have mental capacity. It allows you to choose who should make decisions and to include preferences or instructions about how they should act.
Deputyship is generally required when somebody has already lost mental capacity without making a valid LPA. A relative or other suitable person must apply to the Court of Protection, which decides whether to appoint them and what authority they should receive.
The deputy may need to pay application and supervision fees, submit reports and comply with ongoing Court of Protection requirements. The process also gives the person who has lost capacity less control over who is appointed.
Making an LPA in advance is generally simpler and allows you to choose your own attorneys. However, deputyship provides an important legal route when an LPA can no longer be created.