An interjection is a word that shows excitement or emotion. They are not grammtically connected to the rest of the sentence. For example: "Hooray! We won!", "Wow, I love these socks", "Yuck! This tastes awful!" Some other interjections are "Oops, bravo, congratulations, dang, wow." I hope this helps. :)

en.wikipedia.org/wiki/Interjection