Whichever style of bike you decide on
However the vast majority of people probably just want a bike to ride around their local town or in the park. In this case something called a 'hybrid' bike is the best option, as this style of bike combines elements from both road bikes and mountain bikes. Hybrids are suitable for both flat pavement and slightly bumpy terrain, so you can have the best of both worlds and won't be limited to cycling only in particular areas.
Whichever style of bike you decide on, there are a couple of basic checks to carry out before making your final purchase. Make sure you have a go on the bike so you can ensure it's the right size for you - you should be able to turn the handlebars easily and place each foot firmly on the ground. Also check whether the retailer you're buying the bike from will build it for you - good ones will throw in a build for free so you can be sure the bike is study and safe.