Even if you haven't been on a bike since childhood, you can start again. Bikes have changed a lot in the past 20 years, so be sure to get a bike that fits your style. There are different types of bikes and levels of biking difficulty. Some bikers prefer road bikes for the casual ride down city or country streets. Touring bikes are meant for long distance travel.
Mountain bikes are better equipped to handle rough terrain.
And racing bikes are used by those who compete in demanding bike races. There are also hybrid bikes which can be used in more than one setting. If you're not sure what type of bike to get, go to a bike shop and ask a pro for some recommendations. Many bike shops will even let you try out the bike before you buy it. Check to make sure the bicycle is the right height for your body.