The correct term for the item in question is the 'tread,' which is part of the tire... when the tread on the tire is worn out you replace the tire. You can buy a new tire for between $12 and $150. The $12 tire is not the best but will work, and the $150 tire is purely for racing. For around $30 - $60 you can find a good quality tire that has good resistance to punctures, rolls smoothly and fast, and is reasonably lightweight. Tires for hybrid bikes are called '700C' tires and are very common.
A bike shop will probably charge you $10 - $15 plus the price of a tire to install a new tire. You can also learn to do it yourself fairly easily.