Downhill - Whether you picked up skating to break the sound barrier with supersonic speed, or you commandeered your brother's abandoned skateboard as something to do with friends, now you're here. Now you're ready to bomb hills, practice pre-drifting, get footage, and get the adrenalin rush of your life. To go fast and stay in control you want a big wheel with a lot of contact with the pavement. The softer wheels are grippier, but eventually the wheel will lose speed if it is too soft. Cores in downhill wheels can be vented, centered, or offset depending on what you are looking for. It all comes down to the quality of 'thane under your board and your ability to rail a corner.
Carving/Cruising - For cruising park trails, taking big turns through your neighborhood, and general transportation riding; carving/cruising wheels meet the needs of many different skate disciplines. They fall in the middle of the size scale so you can ride down medium grade hills with some of the stability bigger wheels offer, but have the faster and larger range of motion of smaller wheels. Often, this category is great for beginners because the wheels tend to be softer, making them grippier. If you are looking to try slides look for wheels with a stone ground finish and/or a rounded lip. If your daily shredding includes a hill or two, try some bigger cruiser wheels with a square lip. No matter what you choose, carving/cruising wheels are going to be fun!
Centerset - Centerset wheels have cores that are placed directly in the center of the wheel, equidistant to the outer edge of each lip. This core placement style gives the most amount of grip because it creates a very large inner lip.
Another advantage of centerset wheels is that they can be flipped inside out to promote even wear and a longer lifespan. For this reason, many freeride wheels have centerset cores paired with small contact patches and round lips.
Square Lip - Square lips provide the most grip and allow you to carve deeper and corner tighter without worrying about losing traction. Square lip wheels are generally preferred for downhill riding.
Smooth - Smooth wheels have a shiny coating on their surface that is commonly referred to as its skin or mold release. Smooth wheels are generally preferred for their grip and traction.
Race Formula - This is Sector 9's fastest and most evenly wearing urethane compound.