It's quite a broad church. Ranges from the big closed roads, timing chip equipped affairs to an open ride put on by a club that they decide to call a Sportive. I've done a couple of
Evans Ride it Sportives which are sort of middle ground.
It depends what you want out of it.
My main reason for doing these things is if some friends are doing it, it can provide a focal point for meeting up, preferably with a nice route that's convenient to get to. Others may have different reasons. You may have your eye on a challenging route and may want the structure of an event to give you some motivation. You may fancy just having somewhere to park at the start/end. Some sportives list finishers in time bands, and you may want to or challenge yourself, or impress your friends, by finishing in a faster band.
Also have a look at Audaxes on
www.aukweb.net. Tend to be longer (shorter routes do exist, but the bread-and-butter is the Brevet Randonneur, which is 200k). But basically, it's just riding your bike along the road, at the same time as some other people. Same as a sportive. They're not very different except at the extremes where they are very different indeed (an extreme example of a Sportive being Ride London 100, and extreme example of an Audax being London-Edinburgh-London).
