In StarCraft II, the Protoss structure that produces Zealots and Stalkers is the Gateway.
A Gateway is the basic Protoss ground-unit production structure. It can train Zealots, Stalkers, Adepts, and other ground forces depending on the game version and available technology. With the Warp Gate research, a Gateway can transform into a Warp Gate and produce units at powered locations.
The Warp Gate mechanic allows Protoss players to reinforce armies quickly near Pylons or Warp Prisms rather than waiting for units to walk from the main base. This gives Gateway placement and power coverage strategic importance beyond simple production capacity.
The Gateway is not the same as the Cybernetics Core, which unlocks key technology, or the Nexus, which is the Protoss command structure. A Warp Prism can transport units and provide power, but it does not replace the Gateway as the production structure.