menstural cup users???

So I have never used this or am very knowledgable when it comes to a menstural cup or diva cup as some say. I'm currently expecting so I do not have to worry about it right yet but I am considering trying it out after I deliver and have the okay. A few questions I have is how does it stay in place to where you can easily remove it? My fear is that I will use it and it get stuck or something... Can anyone that uses these shed some insight on this topic.