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Glossary

What is a foundation model? Explained

A plain definition of a foundation model, how it differs from an LLM, when a smaller model fits, and how companies adapt one to their work.

Updated

Definition

Foundation model

A foundation model is a large AI model trained on broad data that can be adapted to many different tasks. One model serves as the base, and each business use is built on top of it.

In short: One broad base model, adapted to many tasks.

What a foundation model is in plain words

One model per job

  • Built for a single task
  • Needs its own training data
  • Starts from zero each time

Foundation model

  • Learns broadly first
  • Adapted to many tasks
  • Reuses one shared base

Older AI systems were built for one job each. A foundation model flips that: it learns from a huge range of data first, then gets adapted to specific work.

Stanford HAI stresses that these models are not only about text. They can also be trained on images, video and other kinds of data.

IBM Research gives a sense of the payoff. With pre-trained models, a language task needed about 100 times fewer annotated examples than before.

Put simply, if you ask what is a foundation model in practice, it is the shared starting point that saves you from training everything from scratch.

Foundation model vs LLM

  • Foundation model

    Broad base model, many data types.

  • LLM

    A foundation model focused on language.

  • Multimodal

    Combines text, images and audio.

  • Frontier model

    Among the most capable at a given time.

A large language model is one kind of foundation model. IBM describes LLMs as deep learning models trained on very large amounts of data to understand and generate language.

So the foundation model vs LLM question has a simple answer: every LLM is a foundation model, but not every foundation model is an LLM. A multimodal foundation model also handles images or audio.

You will also hear frontier model. That term points to the most capable models available at a given moment, while foundation model describes the base-and-adapt design.

For the language side, see large language model. For the data side beyond text, see multimodal AI.

Small language models and when they fit

Small model fits

  • Narrow, repeated tasks
  • Data must stay in-house
  • Speed and low cost matter

Larger model fits

  • Open-ended questions
  • Broad general knowledge
  • Mixed, unpredictable tasks

A small language model is a compact language model with far fewer parameters than the biggest ones. For comparison, GPT-3 had 175 billion parameters, and that is the scale small models avoid.

Smaller models run on lighter hardware, answer faster and can stay inside your own systems. That helps when cost, speed or data privacy matter more than broad knowledge.

A small language model fits narrow, repeated tasks such as sorting emails or extracting fields. Open-ended work that needs wide knowledge usually calls for a larger model.

Check the right size against the job before choosing. Our AI integration work starts with that fit.

How companies adapt a foundation model

  1. 01

    Prompt

    Give clear instructions and examples.

  2. 02

    Retrieve

    Connect the model to your documents.

  3. 03

    Fine-tune

    Train further on your own examples.

Most companies never train a base model. They adapt an existing one, and there are three common ways, from lightest to heaviest.

Prompting gives clear instructions and examples. Retrieval connects the model to your own documents so answers use your facts. Fine-tuning trains the model further on your examples.

Start light and add effort only when results demand it. For the retrieval route, read retrieval-augmented generation.

Our data

What AI answers when buyers ask

We asked ChatGPT, Gemini and Perplexity 10 buyer questions about custom AI development. They named 100 companies, and 80% appeared in only one of the three.

CriterionChatGPTGeminiPerplexity
Companies named433546
Sites cited mosthatchworks.com (3 of 10)vellum.ai and mindstudio.ai (3 of 10)rtslabs.com and netguru.com (4 of 10)

Nexum measurement, October 20, 2026, via DataForSEO: 10 buyer questions to each AI, US English, 30 answers in total. 4 companies appeared in all three. Google showed an AI Overview for 9 of the 10 questions.

FAQ

Foundation model questions

  • A foundation model first learns patterns from very broad data. Teams then adapt it to a task through prompts, retrieval from their own documents, or extra training on examples.
  • Yes. A large language model is a foundation model built mainly on text. Other foundation models also use images, video or audio. See generative AI for how they create content.
  • Small language models are compact versions built for narrow work such as classifying messages or pulling fields from forms. The common trait is a much smaller size than the largest models.
  • An LLM is the general category of large language models. GPT is one family of models within that category, so every GPT model is an LLM but not every LLM is a GPT.
  • Not to train one. You use an existing model and adapt it to your process. Our AI strategy guide covers choosing where to begin.

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