As with cars there are many different types of bike depending on what job you would like them to do. Do as much research as you can to get the right bike for you and the type of cycling you want to do. Here’s a brief rundown of the three main types.
Mountain bikes tend to have knobbly tyres, usually suspension at the front and sometimes at the rear, their geometry is generally a comfortable position neither too up right or leaning forward. They are specially designed for off road use, although they can be used on road they will be slower than other types. Mountain bikes are perfect for cycling through the forest, on a hill side or places where you require lots of grip and freedom of movement.
Road/racing bikes are specially designed for travelling at faster speeds along tarmac roads. They tend to have larger wheels then mountain bikes, skinny tyres that are fairly smooth, curled drop handle bars and a geometry which sits you leaning forward for better aerodynamics. These are a great option if you require or would like to cycle longer distances within a period of time, i.e. travel to/from work, as they are faster and more efficient.
Hybrids come in a variety of different forms but are quite often somewhere half way between a mountain bike and a road bike. They tend to have tyres that are neither too knobbly or smooth, quite often a more relaxed comfortable geometry than a road bike and will sometimes have racks in which to carry bags on the bike. These are a good option if you are looking for a general bike which will be good on cycle paths, off road paths and road. Great for day to day cycling and for cycling holidays where you need to carry clothes/equipment.
As with anything you get what you pay for, a £70 bicycle from a supermarket or similiar will generally be very heavy, will only be suitable for gentle, basic cycling and might not last very long without maintenance problems. For a good quality brand new adults basic mountain bike, expect to pay upwards of £300. The second hand market is also a great option, ensure you ask questions about their reason for sale and only purchase if you are satisfied.