Hints are helpful advices given to the player during gameplay. The kind of advice given varies depending on the location. They give the player useful information to help you in situations such as an obstacle or a new gameplay feature.
List of Hint types
Hint Orb
Making their first appearance in Sonic Adventure, the Hint Orb is a floating red and white sphere of light that hovers just above the ground. On contact they will circle the character while giving advice that pertains to the situation the hero has to overcome. Sometimes Knuckles will find a Hint Orb which will show him exactly where the piece of the Master Emerald is located.
The Hint Orb is also Tikal's spiritual form. Evidence is that the voice of the Hint Orb is her own and when Perfect Chaos threatened to destroy the world again, she appeared to Sonic as a Hint Orb before her regular appearance.
Hint Box
The Hint Box is a variant of the Hint which appears in Sonic Adventure, Sonic Adventure 2 and their remakes. They resemble floating computer monitors. Unlike regular hints, they will not activate by touch. Instead, they are meant to be talked to by pressing the Action button when close up to them.
Omochao
Omochao is a robotic Chao with a propeller on its head. Its name is a portmanteau of the Japanese word omocha, meaning "toy", and Chao. He replaces the Hint Orbs in Sonic Adventure 2 dispensing a variety of advice. Omochao also had other uses such as a being used as a throwing weapon to sometimes humorous results. Omochao can also be attacked (whether it's accidentally misfiring or purposely) and will say quotes like "That hurt!" or "I'm not gonna help you any more!"
Hint Ring
Hint Rings appeared for the first time in Sonic Heroes. On contact, the playing character or companion (or sometimes even a narrator) will tell advice for the situation. The Hint Ring originally was a question mark centered in a rainbow colored sphere. But later series became a golden question mark with colorful orbs circling it vertically. Since Sonic Heroes, Hint Rings have become the common variation of the hint objects.