A Bridge Rectifier is just a rectifier as commonly spoken of in audio and electronics.  it's not for more or less power.  it's for converting AC into DC which nearly any electronic thing that plugs into a wall needs to do.

it's a pattern of 4 diodes "one way valves" that "sorts" the incoming power into positive side and negative side.  it does this to the incoming power which is alternating between positive and negative.

Wikipedia has nice pictures and explanations of different types.

They can be implemented with solid state diodes or inside tubes (rectifier tubes which contain 2 or 4 one way "valves")