How do I disconnect two points of a bezier curve? I am fairly new to Blender and I would love some help with this problem. I modeled a bezier curve a couple of days ago, and then wanted to change it.

I know how to connect two vertices of a bezier curve by pressing F to fill it, but how unfill two vertices, such as to disconnect them?

Here are some pictures to help out with my scenario. Picture 1 shows the two vertices I want to fill. Picture 2 shows both the vertices I wish to disconnect. Thanks!

P.s. What is this red line that showed on my curve? (picture 2)
To close a curve (make it Cyclic), select the first and last segments and press Alt+C.

To open a closed curve at the press Alt+C again.

To open a curve at any point that is not the start and end of the loop, select two control points and press Delete (or X) and select Delete Segment