Traditionally, torque converters are considered "black magic". You can't see in them, you can't open them; therefore, you can't inspect them nor can you "fiddle" with them. That's probably the prime reason people are mystified by torque converters. Because we car guys, gear heads, techno-geeks (whatever we are), can't get inside to see just what's happening in there. Once you understand the basics of them, selecting your torque converter becomes much easier. And not such a mystery. So, this is what is inside a torque converter:

The Impeller
Also known as the pump or driving member; the impeller is driven by the engine. The many curved vanes force fluid outside the converter, creating centrifugal force when spun by the engine.

Stator (w/ One Way Roller Sprag)
The reaction member is a smaller vained rotor located between and turbine. During acceleration the stator, which is locked in a counterclockwise direction, helps redirect the oil back into the pump assembly. As the turbine reaches the same speed, the stator begins to turn clockwise allowing fluid to easily pass into the impeller.

Also known as the driven member, looks very similar to the impeller because of its shape and curved vanes. The outer blades of the turbine receive the force fluid of the impeller. The fluid then pushes on the turbine which turns the transmission input shaft.

Clutch and Damper Assembly
Only lock up units, this assembly is what mechanically links the turbine to the front cover. The clutch assembly, when activated by oil pressure, produces a one to one ratio between the motor and the transmission. this in turn lowers engine rpm's and increases fuel efficiency.

Front Cover
The front cover is what mechanically links the pump to the crankshaft of the motor. It also acts as the friction surface on lock up units.

Torque Converter Fact & Function

First, you need to understand the functions of a torque converter. One of the jobs of the converter is to act as a fluid coupling from the motor to the transmission. Another, and a very important function, is torque multiplication. What remains is stall speed, a very misunderstood term. Stall speed is directly related to the amount of torque your engine produces (the greater torque, the higher the stall speed). For example, a converter with a 2800 to 3200 rpm rating might provide approx. 3200 rpm of stall speed behind the big block making 500-plus lbs of torque and in a small block with less torque it's possible to only have a stall speed of 2800. Without knowing how much torque your engine produces, you cannot know how much stall speed a converter is capable of.

Important Factors That Affect A Converters Stall Speed

    Vehicle Weight
    Vane/Fin Angle
    Impeller to Turbine Clearance
    Stator Design
    Torque Rate
    Converter Diameter
    Gear Ratio
These can be some of the biggest questions you have when looking for a converter. The best solution to any of your questions is to speak with a qualified technician at a high quality company.