A draw call is a single instruction from the CPU telling the GPU to render a set of triangles with specific settings. Each draw call carries overhead: the CPU must validate state, set up shader parameters, bind textures, and issue the command. A scene with 10,000 individual draw calls can become CPU-bottlenecked even if the GPU has plenty of power to spare. Optimization strategies include batching objects that share the same material into a single draw call, using texture atlases to combine multiple textures so objects can share materials, instanced rendering for repeated objects, and modern approaches like indirect rendering where the GPU itself decides what to draw. The shift to modern graphics APIs like Vulkan and DirectX 12 gave developers more direct control over draw call submission, reducing per-call overhead significantly.