All glass contains Silica, also known as Quartz, an abundant mineral on our planet. It's everywhere underfoot and in heavy concentrations at the beach. We've invented a variety of different things to make with this stuff, here's just a few.
Fused Quartz Glass
This is the pure silica made into glass form. Usually used for lamp tubes, heater tubes and other high heat applications. It can withstand up to 1500°C and doesn't expand/contract too much when heated/cooled.
This is the heavy duty stuff we've seen as beakers in science class and corningware in our mom's kitchens. It's composed of 81% silica with 12% boric oxide and some other stuff. This kind of glass also has low "coefficients of thermal expansion", so it doesn't break when heated.
Also known as soda lime silica glass, this is the world's most common glass. It's made of 72% silica with 14% sodium oxide and 10% lime. We use it for virtually all glass you see in an average day. The windows in your home are made of it. Using a heating process to 'temper' it, we make it stronger and safer. Tempered or 'toughened' glass is used for windshields, many commercials windows and walls, aquariums, showers and more.
You've seen cabinets of this stuff at your grandma's. Because of its high density, it has a high refractive index, making the look of glassware more brilliant. It's 50% silica with 25% lead oxide and 12% potassium oxide.