These are large balls of mostly hydrogen and helium that are engaging in nuclear fusion that become visible in the sky at night. They are fusing hydrogen to helium which creates the energy the core of the star needs to prevent it from collapsing into itself, and also to create radiation and the light the star produces. The closest star to Earth and the only star that can be viewed with detail from Earth is the Sun, with the next closest star to Earth being Proxima Centauri 4.24 light years away.
Stars are formed in clouds of gas and dust called a nebula. As energy inside the nebula starts to build, it forms a collection that will then begin to collapse into itself because it has enough mass to have gravitational pull. In the center of that collapsing cloud is what’s called a protostar which will eventually become a star, and it takes about ten million years for that protostar to form. After a few million more years the protostar is stable and ready to begin its life as a star which means changing from one type of star to another before ultimately fading into nothing or becoming something else entirely.
Below is a list of the types of stars which represents not only different types of stars but also different phases of a star’s life: