Perhaps there's no such difference, but I'm looking for a first organized ride to register for to create a goal for myself. But, I want to make sure that I'm getting into a ride where I'm not completely outclassed. (Coming in last is OK, but coming in last by an hour isn't.)

Are there certain key phrases to look for when browsing the various rides? (Like in running, they call them "fun runs", but I'm not finding anything like that. I'm finding some "family friendly", but they're only 12 miles or so.

Is there a particular length that would be most appropriate? Obviously I'm not going to go for a full century, but I'd like a metric half-century on semi-flat terrain.

Any ideas to help me choose a "safe" first ride?