"I am a butterfly."
Translation:Sono una farfalla.
The word essere is a verb, it means "to be" When using it, you conjugate it: Io sono (I am) Tu sei (You are) Lui/Lei è (he/she is) Noi siamo (we are) Voi siete (You are) Loro sono (they are)
Since its just a verb, it can be used for both humans and animals:
Io sono l'uomo. I am the man.
L'ape è un insetto. The bee is an insect. Io sono un ape. I am a bee.
Also, you can choose to not use the pronoun (io,tu,lui,lei,noi,voi,Loro) and just say the conjugation of the verb, they would both make sense.
Sono un ragazzo. I am a boy.
È un uomo. He is a man.
Sei una bambina. You are a girl. (younger than 10 usually is bambina/bambino)
If you are a Spanish speaker, you might be thinking of two verbs "to be" in español, ser and estar. Italian has something somewhat similar with essere and stare. Here's a couple links: https://www.mytutor.co.uk/answers/7355/A-Level/Italian/What-is-the-difference-between-the-verbs-essere-and-stare/ and https://grammar.collinsdictionary.com/us/italian-easy-learning/essere-and-stare The verbs come from Latin esse and stare, but each Romance language handled the division of labor for the verbs differently.