An elliptical galaxy is a type of galaxy on the Hubble sequence classification scheme.
It's estimated that 60% of all galaxies in the observable universe are elliptical galaxies.
There are eight main types of elliptical galaxies, and they are classified between E0, E1, E2, E3, E4, E5, E6 and E7.
The best way to understand the eight main types of elliptical galaxies is simple, an E0 will have a near perfect circular shape, while a E7 will be very stretched out. Everything classified between E0 and E7 is a variant of both extremes.
The shape of an elliptical galaxy is ellipsoidal without any noticeable features.
The luminosity of elliptical galaxies can vary quite a bit. Some are as bright as 10 quadrillion times our sun (supergiant elliptical galaxies) or as dim as a 100 thousand times our sun (dwarf elliptical galaxies).
An elliptical galaxy has very low, if any active star formation, which is due to their lack of dust and gas that would support the formation of a star.
The elliptical galaxy IC 1101 is the largest galaxy in the observable universe, with an estimated diameter of 2,000 kilolight-years.
The elliptical galaxy Maffei 1 is the closest elliptical galaxy to the planet Earth.
An example of an E1 elliptical galaxy is Messier 105, also known as NGC 3379.
An example of an E2 elliptical galaxy is Messier 49, also known as NGC 4472.
An example of an E5 elliptical galaxy is Messier 59, also known as NGC 4621.