Silicone a complex compound

It's a lot like the familiar carbon-based grease,
but the carbon has been replaced with silicon.
(Silicon is a lot more abundant than carbon.)

Silicon an element
The second most abundant element in the Earth's crust.  You rarely see it in this, the pure form.  It's the most common semiconducting material, the stuff of computer chips.
Silica a mineral, SiO2
The most abundant mineral on the face of the Earth. It's silicon dioxide, here in the form quartz.  (This specimen is amethyst quartz from Brazil.)  Most sand is mostly quartz.