What is a large language model (LLM)?

A large language model (LLM) is an artificial intelligence system designed to understand and generate human language by training on massive amounts of text data. These models use neural networks, specifically architectures like the transformer, to process sequences of words and learn patterns in language. The term “large” refers to their scale: LLMs often have billions or trillions of parameters, which are numerical values adjusted during training to capture relationships between words and concepts. For example, models like GPT-3 or Llama 2 analyze text to predict the next word in a sequence, enabling tasks like answering questions or writing code. Their effectiveness stems from exposure to diverse data sources, such as books, websites, and technical documentation, allowing them to handle a wide range of topics and styles.

LLMs work by breaking text into smaller units called tokens (e.g., words or subwords) and analyzing how these tokens relate to one another. The transformer architecture uses mechanisms like self-attention to weigh the importance of different tokens in a sentence, enabling the model to focus on relevant context. During training, the model adjusts its parameters to minimize prediction errors, gradually improving its ability to generate coherent and contextually appropriate outputs. Developers often interact with LLMs through APIs (e.g., OpenAI’s GPT-4) or open-source frameworks like Hugging Face’s Transformers, which provide pre-trained models that can be fine-tuned for specific tasks. For instance, a developer could use an LLM to automate documentation by feeding it code comments and generating summaries, or to create a chatbot that understands technical queries about an API.

While LLMs are powerful, they have limitations. They can produce plausible-sounding but incorrect answers, especially when dealing with niche or rapidly changing topics. For example, an LLM might generate outdated code examples if its training data doesn’t include recent framework updates. Additionally, their outputs can reflect biases present in training data, requiring careful validation. Developers should combine LLMs with traditional methods—like rule-based validation or database lookups—to improve reliability. Computational costs are another consideration: running large models locally may require specialized hardware, while cloud-based APIs incur usage fees. Despite these challenges, LLMs offer practical tools for tasks like code completion, error message interpretation, or generating test cases, making them valuable when used with awareness of their strengths and weaknesses.