The concept of antimatter in physics does indeed involve the existence of antiparticles, which are particles that have the same mass as their corresponding particles but opposite charges. For example, the antiparticle of an electron is called a positron, which has a positive charge. Antiparticles are a consequence of certain symmetries in the laws of physics.
Antigravitons, on the other hand, are theoretical particles that have not been observed or confirmed Gravitons themselves are hypothetical particles that are thought to mediate the force of gravity, similar to how photons mediate the electromagnetic force. The existence of antigravitons is a subject of speculation and ongoing research in theoretical physics, but their properties and behavior, if they exist, are not yet well understood.
It's important to note that while antimatter has been experimentally observed and studied, antigravitons remain in the realm of theoretical physics and have not been detected or confirmed through experiments at this time. Our understanding of the fundamental forces and particles is continually evolving, so future discoveries may shed more light on these topics.