Action Types

Tape Check
Tape check is the preferred arrangement  and all new upright pianos use this type. 
 
Spring and Loop
   Spring & Loop is an early type of action. When in very good order it works excellently, although it has little resistance and feels very light to play.
You are unlikely to find one in good order.
Loop through the Jack.
Loop through the jack has to be mentioned as it has been confused with Spring & Loop actions.
Loop through the Jack has an extra spring to hold up the Butt so that the jack can return much faster. 
This is fitted to Tape Check actions and will be found on top quality pianos only.
Slide Escapement.   Slide Escapement is another version of the Tape check action with a slide escapement for the jack. It is not widely found and does not have the control of the standard Tape Check action.