With skepticism and open-mindedness, they both revolve around the fact that they don't "confine" themselves in an idea.
However, the difference comes with the means of not confining themselves. With skepticism, you are questioning that idea and essentially, taking that idea with a pinch of salt. With open-mindness, however, you aren't questioning the idea but rather are willing to open yourself to other ideas aside from that singular idea.
Here's an example (it's simplified, but you should understand the difference):
Skepticism: I used to believe in idea A, however after scrutinizing it I'm starting to doubt idea A.
Open-mindness: I believe in idea A, however I want to understand ideas B and C as well.
