GPT models generate human-like text for various applications. GPT architecture uses transformer decoder with self-attention mechanism. Training on massive text corpora enables language understanding. guides model output toward desired responses. Temperature controls randomness: lower values for focused output. Top-p sampling selects tokens with cumulative probability. Max tokens limits response length. Few-shot prompting provides examples in the prompt. Fine-tuning adapts base models to specific domains. Applications include content generation, chatbots, and code completion. Summarization condenses long documents into key points. Translation between languages with natural output. Question answering extracts information from context. The GPT family includes GPT-3, GPT-4, and open-source alternatives. InstructGPT improves instruction following through RLHF. API access through OpenAI and other providers. Deployment considerations include latency, cost, and content filtering. Prompt injection attacks require security consideration. Ethical use requires transparency and bias mitigation. GPT represents a significant advance in natural language processing.