A parallax is the apparent displacement of an astronomical object when viewed from different positions. The most important parallax in astronomy is stellar parallax. The more distant the star, the smaller is its parallax, and so parallax can be used to calculate distances. The parallax of the nearest known star, Proxima Centauri, is 0.762 arc seconds, indicating a distance of 4.3 light-years. The astronomical unit of distance, the parsec, is the distance of a star having a parallax of 1 arc second.
Stellar evolution is the creation and termination of stars.
A star begins as a Protostar. A protostar is a cloud of hydrogen molecules in space. Next the star becomes a Red Giant. A Red Giant is created through the proton-proton cycle. The process starts when the hydrogen molecules in the cloud fuse together to create helium.