Hi Jeff,
When you mount your TLA flash on a Contax camera and switch it on the camera defaults to its flash synch' speed setting - usually 1/125, though it can be 1/60 or 1/250 depending on the model.
If you then select Exposure Lock on the camera, providing the metered reading for the given film speed and aperture set does not exceed the flash synch' speed the camera will expose the shot at the speed it would have used if the flash was not fitted. So instead of it giving your synch' speed of 1/125, it may set 1/30 or 2 seconds for ex&le and fire the flash as soon as the shutter opens. This is commonly known as Slow Synch' Flash, Daylight Balanced Flash, Fill In Flash, or on some compacts - Night Portrait Mode. This feature is very, very useful for a whole variety of photographic situations.
As you point out Second Curtain Flash is available on some Flash / Camera combinations - this fires the flash just before the shutter closes rather than as the shutter opens and is used for capturing blurred movement shots.
Clive