Render pass
A bounded rendering phase in modern graphics APIs that declares up front which buffers it reads and writes, so the driver can lay out memory optimally.
Old OpenGL let you draw anything, anywhere, at any time; Vulkan (2016), Direct3D 12 and Metal invert that and make you describe a pass in advance — its colour and depth render targets, whether each should be loaded or cleared (load/store), and what becomes of the result afterwards. The driver no longer has to guess.
The payoff is largest on mobile GPUs with a tile-based architecture: if the hardware knows an intermediate buffer is only needed inside the pass, it can keep it in fast on-chip memory instead of spilling to slow main memory. Chaining subpasses lets a technique like deferred shading run its geometry and lighting steps without ever touching external memory in between.