Half ropes are used in pairs but clipped independently to protection. They are designed to stretch one at a time to cushion the shock of a fall. Half ropes are beneficial on meandering pitches where alternating rope clips helps reduce rope drag. They are also popular for alpine climbing, where you need two ropes to rappel off the peak. Half ropes are marked with a "1/2" inside of a circle.
Some Edelweiss ropes are rated for not just one option (single, half, or twin) but instead are dual or triple rated for use in a variety of applications.