Was it said by someone who is not present at trial? Remember "statements" include oral and written assertions as well as nonverbal conduct.
A statement offered in evidence to prove the truth of the matter asserted in the statement is hearsay. Example: "Sam told me he saw Diane run out the door."
If you're dealing with an out-of-court statement offered to prove the truth of its content, that's hearsay. But, it might still be admissible.
Some of the most common exceptions are:
Have they refused to testify? Are they exempted because of some type of privilege? Are they dead, or seriously ill?