A cycle sportive is a mass participation cycling event which is open to all comers.
They are usually events that are aimed at road bikes and normally will have several choices of route so that riders can choose the distance that they want to ride.
If you enjoy riding a bike, then almost certainly you will enjoy riding in a sportive!
Taking part in a sportive is as enjoyable and pressure-free as you want to make it.
There's no competition with other riders, you ride at your own pace, to achieve your own personal goals and enjoyment whilst taking in the scenery. If you are new to cycling then completing the distance might be your personal challenge.
Sportives are a great opportunity to meet other riders and ride with a group at your pace too.