An AI agent is a system that uses a large language model as its brain and equips it with planning, external tools, and memory so it can break down a goal, call tools, and keep executing until the task is done. If a chatbot is "a mouth," an agent is a digital employee that can actually do the work.
Prompt engineering is the practice of designing your instructions so a large language model reliably produces the result you want. With the same model, someone who asks well can easily get ten times better output than someone who does not.
An LLM works by predicting the next token from the context it is given. The clearer that context, the less room the model has to guess. Writing a prompt is like briefing a brilliant new hire who knows nothing about your business: you have to explain the background, the goal, the requirements, and the standards.
A large language model (LLM) is a Transformer-based AI system trained to generate text by repeatedly predicting the next token — the same technology behind ChatGPT, Claude, Gemini, and DeepSeek.
Think of an LLM as a world-class "sentence completion" engine that has read enormous amounts of text. When you send a prompt, it does not look up an answer in a database. Instead, it calculates, token by token, what is most likely to come next.
