What is a decaritive sentence?

There's no such thing as a "decaritive sentence." It's likely a typo. The correct term is declarative sentence.

A declarative sentence is a sentence that makes a statement. It states a fact, opinion, or belief. It typically ends with a period (.).

Here are some examples of declarative sentences:

* The sun is shining today. (Fact)

* Chocolate is the best flavor of ice cream. (Opinion)

* I believe in the power of kindness. (Belief)

Let me know if you have any other questions about grammar!