Straightforward and truthful talk might be described with the adjective candid. If you're always candid, your parents will know that they can trust you.
A serious-minded politician might suggest engaging in a "candid discussion" about a complicated topic like health care or the environment, because candid means "open" or "frank." Remember that TV show Candid Camera? It was called that because its hidden cameras supposedly showed a candid view of reality. In photography, candid has become a noun meaning "an unposed photo." The word comes from Latin candidus, meaning "white," which was later extended to mean "pure." Candid talk provides the pure, unvarnished truth.