# Weights, Parameters and Model Families — Local LLMs with Ollama & llama.cpp

Source: https://www.skillbyai.com/en/local-llms/ll-weights-params

> Read a model name like qwen2.5:7b-instruct and know what the size, family and instruct suffix mean.

## Decoding a model name

Open-weight models are published by labs in **families** (Llama, Qwen, Gemma, Mistral, Phi and others), each in several **sizes** measured in parameters: 1B, 3B, 7B, 8B, 14B, 70B and so on. More parameters generally means better knowledge and reasoning but more memory and slower generation. Most families ship two flavours. A **base** model was only pre-trained to continue text; ask it a question and it may continue with more questions. An **instruct** (or chat) model was further fine-tuned to follow instructions in a conversational format, which is what you want for assistants. Some names also carry the **context length** or a specialty such as *coder* or *vision*. Finally, check the **licence**: open weights does not always mean free for every commercial use, and each family has its own terms.

## Engine size on a bike

A 100cc bike and a 350cc bike from the same company share a design, but the bigger engine pulls harder and drinks more fuel. Model sizes within a family work the same way: same architecture, more parameters, more capability, more memory and power.

## Base vs instruct trap

If a model rambles, repeats your prompt or ignores instructions, check that you pulled the instruct variant and that the correct chat template is applied. A base model behind a chat UI is a common beginner mistake, and it looks like the model is "dumb" when it is simply the wrong flavour.

**Quiz:** You want a local assistant that answers questions in a chat. Which variant should you choose?

- [ ] The base model, because it is the original
- [ ] Any variant; they behave identically
- [ ] The largest model regardless of RAM
- [x] The instruct (chat) fine-tuned variant

*Answer:* The instruct (chat) fine-tuned variant. Instruct models are trained to follow instructions in a chat format. Base models only continue text and often do not answer questions directly.