If by this question you mean what kinds or armour is there in Fallout 3 there is a varied answer.
- Standard clothing worn by wastelanders that offer little protection but provide an Agility bonus.
- Multiple variants of Raider Armour that offer low protection and can be found on any raider.
- Leather and Metal Armour make their return from previous Fallout games offering medium protection and can be found in the Wastes or bought from vendors.
- Combat Armour and their unique variants. Worn by high-priority characters and (depending on your Karma) Talon Company Mercs. A unique variant is offered to the player upon completion of Reilly's Rangers. It offers high protection.
- Various versions of Power Armour. This is highly advanced armour utilising hydraulics and electronics to greatly increase the wearer's strength. Power Armour is worn by Enclave Soldiers, Brotherhood of Steel members, Brotherhood Outcasts and various important story characters. Specialised training is needed to wear it and is offered the the player near the finale of Fallout 3. Power Armour offers the best protection in the game.
I hope this answers your question.