Which two pressures comprise the outward push resisting stellar gravity?

Thermal Pressure and Radiation Pressure

The outward force necessary to counteract gravity is generated by nuclear fusion occurring in the star's incredibly dense and hot core. This outgoing push is comprised of two distinct but related components. Thermal Pressure arises because the extreme heat excites the plasma particles (ions and electrons) to move at extremely high velocities; this rapid, chaotic motion generates significant pressure pushing against the overlying layers. Concurrently, Radiation Pressure is created by the massive output of high-energy photons produced during fusion. As these light particles stream outward from the core toward the surface, they collide with surrounding matter, imparting momentum and effectively pushing the stellar material away from the center, contributing to the necessary inflation.