Single-Stage Trigger
A trigger with no take-up before the break. Pressure builds against a wall and the sear releases when the set weight is reached.
A single-stage trigger moves essentially not at all until it fires. You build pressure against a solid wall, and when you reach the trigger weight the sear lets go. There is no preliminary slack to take up first.
Benchrest and many precision shooters favor single-stage triggers set light and crisp, because there is nothing between the finger and the break to disturb the rifle. The contrast is the two-stage trigger, which adds a deliberate first-stage travel. Whichever you run, consistent trigger pull and a clean reset are what you are really after.