Elements are the basic building blocks of the environment we see. This does not mean, however, that they are indivisible. Elements are the smallest unit of matter that retains its properties. They are composed of one type of atom. The numbers of protons, neutrons and electrons they contain determine their characteristics. The lightest element is hydrogen, which is composed of one proton and one electron. There are 92 naturally occurring elements and many more which are man-made, such as plutonium. Elements combine in various ways to create the world and universe we perceive today.
The most abundant element in the universe is hydrogen, most likely due to its simplicity. Hydrogen serves as the fuel for stars during most of their lives. The stars burn this hydrogen, through fusion, and create helium, which is the second lightest element. As the star, after many years (between millions and billions), burns up all of its hydrogen fuel, the helium that was the byproduct from the above begins to be burned into other, heavier elements. Once the star eventually reaches a stage where iron is produced, there is a lack of energy to counter-balance the force of gravity. The equilibrium is broken and the star begins to contract forming various objects (mentioned in other articles).
As the star explodes, all of the various heavy elements produced in its death stages are expelled into space. These serve as the building blocks for objects such as planets, asteroids and more. This is where the popular maxim, "we are made of star stuff ," comes from.