Large Language Models (LLMs) are a class of foundation models built on transformer neural networks and trained on vast text corpora to predict the next token. That simple objective gives them broad language skills—reasoning over context, following instructions, translating, summarizing, writing code so one general model can power many tasks instead of training a new model for each use case.
Under the hood, LLMs tokenize text, learn dense vector representations (embeddings), and use attention to weigh which parts of the input matter most. During training they learn statistical patterns of grammar, semantics, and world knowledge, which they can adapt with techniques like prompt design, fine-tuning, and reinforcement learning from human feedback(RLHF).
In production, reliability improves when you ground the model in your own data (retrieval or tool calls), constrain outputs to a schema, and monitor for drift, bias, and hallucination.
Example
Think of ChatGPT: it’s a chatbot interface powered by OpenAI’s LLMs like, GPT-4o, GPT-4.1, and now the new thinking model GPT5. You can paste unorganized product brief and ask for “a 120-character PDP title and three benefit bullets,” the LLM reads the text, reasons over what matters, and writes clean copy; if you connect it to your catalog or order system, it can also pull live facts (sizes in stock, delivery windows) and respond with grounded answers instead of guesses.
GPT-4o added strong multimodal skills (text + vision + audio), while GPT-4.1 later improved instruction-following and long-context use—illustrating how the same ChatGPT interface gets better as the underlying LLMs advance. The new GPT5 not only outperforms previous models on benchmarks and answers questions more quickly, but most importantly is more useful for real-world queries, and is also the strongest coding model till date by openAI.
LLM use cases