Hello,
Good initial reading are the KUKA manuals, which you should have received with your robot (if not, I can send you a few) - this will make it easier to understand some aspects.
Basically, KUKA|prc works with the principle that you just queue up commands, mostly movements. There are several types of movement, e.g. linear, PTP, spline, circular (see manual for details) which require different inputs.
It's just essential to know that you need more data than just XYZ to define a robot position - XYZ is enough for a 3-axis CNC machine, a 5-axis machine already requires the definition of XYZ plus a tool axis. With the robot, you at least have to define XYZ, plus tool axis, plus the rotation around the tool axis (in KUKA|prc: orientation). So you either define a position via a plane (fulfills the requirements) or via three points, with the first base point defining the tool center point (XYZ), the second point the tool axis, and the third point the orientation around the tool axis. You can switch between plane mode and 3-point mode by right-clicking a movement component.
Even with the endeffector clearly defined, there are still 8 different ways how a robot could approach that positon (see status/turn in the KUKA manual).
If you want to have the robot follow a line, you either have to divide the curve into many planes, or into many "triplets" of points. Some of KUKA|prc components take care of the work (e.g. divide by distance, which requires a base curve, a guide curve, and an orientation point - it gets the base points from dividing the base curve, the guide points from dividing the guide curve, and the orientation from the point).
Hope this makes it a bit clearer!
Best,
Johannes