A star is A massive ball of gas that generates prodigious amounts of energy (including light) from nuclear fusion in its hot, dense core. The Sun is a star. there are many types of stars:

Main sequence star: stars fuse hydrogen atoms to form helium atoms in their cores. About 90 percent of the stars in the universe, including the sun, are main-sequence stars. These stars can range from about a tenth of the mass of the sun to up to 200 times as massive.

Red giant: A red giant is a star that has exhausted the supply of hydrogen in its core and has begun thermonuclear fusion of hydrogen in a shell surrounding the core. They have radii tens to hundreds of times larger than that of the Sun. However, their outer envelope is lower in temperature, giving them a reddish-orange hue.

Hyper giant: Hypergiants are the largest stars in the universe, usually larger than supergiants. The hypergiant with the largest known diameter is VY Canis Majoris, which is about 2,000 times wider than the Sun (or 2.784 billion kilometers). This is roughly the same diameter as the orbit of Saturn.

Neutron star: Neutron stars are created when giant stars die in supernovas and their cores collapse, with the protons and electrons essentially melting into each other to form neutrons.