Buying your first bike can be daunting. There is a saying in the bike world that n+1 is the number of bikes needed. In other words, you can never have enough! It all begins with one, but which one to start with?
1)The Road Bike
These bikes have narrow tyres, normal in the range of 23-28mm and quite often slick, but you can get a tyre with trend depending on the wet and road conditions. I noticed in the rest of Europe they tend toward the larger more grippy tyre. Drop handlebars allow for various positions. The rigid frame allows more power to be transferred. Suspension and larger tyres will absorb some of the power. There are different frames depend on your a budget you decide want suits you best. Steel, aluminium and carbon.
Use: road, touring and commuting, road cycle clubs, racing and time-trials (not everyone goes aero).
The Mountain Bike
Nowadays, there are many types of mountain bikes with different purposes. The mountain bike is designed for off-road. Generally, have tough heavier frames. They have straight handlebars. The tyres are wider and have more thread. More gears enable you to climb more easily. The modern bike has disc brakes as they offer excellent stopping and control compared to the traditional cantilever brakes. Most have suspension, full-suspension or hardtail (suspension front forks only). I would recommend at least having front suspension (hardtail). Unless you are not going off-road. Apparently, a load of mountain bikes purchased never go off-road
I know I got confused by the range the first time I looked. A good basic mountain bike can take you most places.
Use: off-road, single track, fire roads, downhill, enduro, cross-country (XC), and many more.

Main photo credit: istock windy55 and Hybrid bike picture istock iakovenko.