Instruct model
An LLM fine-tuned to follow instructions (answer questions, do what you tell it) instead of just continuing text.
Raw base LLMs like GPT-3 were good at autocomplete but not "summarize this". InstructGPT (2022) was the first big step toward today's chat models. Today the "Instruct" suffix is common: Llama-3-8B-Instruct.