* Compound: A compound is formed when two or more different elements chemically combine in a fixed ratio.

* Mixture: A mixture is a combination of two or more substances where each substance retains its own properties.

* Element: An element is a pure substance that cannot be broken down into simpler substances by chemical means.

C3H6 represents the chemical formula for Propene, a hydrocarbon. It is made up of the elements carbon (C) and hydrogen (H) in a specific ratio. This fixed ratio and the chemical bonding between the atoms make it a compound, not a mixture or an element.