They are both types of sexual assault. To molest is to make unwanted sexual contact of some sort, while rape is some type of intercourse without consent. Each word's legal definitions vary depending on the state/country.
Also, in general when discussing or mentioning either on the internet, it is considered good form to precede it with a "content warning" for sexual assault, as it is of course a very sensitive subject.
Side note: molest can also technically mean "bother" or "mess with" in more innocent ways. That is not a very common usage, but you'll still sometimes see it on signs like these!