It is commonly believed that the Buddha, also known as Siddhartha Gautama or Sakya Muni, was not the first Buddha. In fact, there were six Buddhas who preceded him, making him the seventh Buddha.

In the Pali canon, the Buddha refers to himself as Tathagata rather than using personal pronouns such as “I” or “me.” This term signifies the Buddha’s transcendence of the human condition and his liberation from the endless cycle of birth and death.

The term Tathagata provides insight into the nature of being a Buddha. It denotes one who is beyond the transitory phenomena of reality and has achieved a state of enlightenment.

The seven Buddhas include three from past eras:

Vipassi, who was known for his supreme insight;
Sikhi, who had a crown protuberance;
and Vessabhu, who was known as the all-protection one.

The four Buddhas from this era are Kakusandra, who destroyed Samsara;
Konagamana, the golden sage;
Kassapa, who protected with light;
and Gautama, the powerful sage.

You can see some more infos in the link below:

https://en.wikipedia.org/wiki/Tath%C4%81gata