Those would be the no tread racing tyres.They range in durability and grip.The cheapest racing tyres are the super-hard slicks which last for ages (usually around 10 laps or so) but take a 2 or 3 laps to heat up and give maximum grip,so you need to exercise caution for the 1st few laps.The most expensive are the super soft slicks which heat up instantly and give maximum grip but the downside is you'll only get a few laps out of these babies.
However,in the beginner league tyre wear isn't a factor and doesn't become an issue until later in the game (very late stages of the amateur league i think).This means if you can afford them and you love your chosen steed,fit her with super soft slicks and watch your lap times tumble. :cheeburga