Original: 51 Pegasi is a yellow dwarf star estimated to be 7.5 billion years old, somewhat older than the Sun, 4-6% more massive, with more metal content and running low in hydrogen.
Simplified: 51 Pegasi is a yellow dwarf star that is thought to be around 7.5 billion years old, which is somewhat older than our Sun. 51 Pegasi is also 4-6% more massive than our Sun with more metal content.