Definite (adjective) or definitely (adverb) means certain, without a single doubt:

We have definite plans to move to New York.

(it is 100% certain that we will move there)

I'm definitely going to the party.

(it is 100% certain that I am going)

This $50 jacket is definitely overpriced. I saw the exact same jacket for $30 in another store.

(it is completely certain that $50 is too much)

The word definitively (adverb) or definitive (adjective) means that something decides an issue, or provides a clear and firm answer/solution to a particular matter:

The evidence from the DNA test definitively proved that Ryan was not the murderer.

The company had been in financial trouble for years, but its definitive end came when it declared bankruptcy in March.

Mythic Creatures That Never Existed But People Believed In Anyway

Kodama

According to Japanese legend, a kodama is a peaceful spirit that lives inside certain kinds of trees. Those who have claimed to have seen a kodama describe it as a small white and peaceful ghost that syncs perfectly with Mother Nature. Nevertheless, according to legend, when someone tries to kill a kodoma (or cut down the tree a kodama lives in), the aggressor will be cursed and many bad things will happen to him. There are also claims of human blood coming out of trees inhabited by kodomas if its cut down but none of these rumors have ever been verified.