Context

1. What Is It?

One-sentence definition

Context is all the information you provide to the model for the current interaction: the prompt, conversation history, references, retrieved documents, and tool outputs.
Context Window is the maximum amount of context the model can handle at one time.

2. How It Works

The easiest analogy is a desk:

• the desk is the Context Window
• the papers on the desk are the Context
• a larger desk can hold more material
• once the desk is full, something must be removed, compressed, or summarized

3. What Is Actually Inside the Window?

1. System prompt
2. Conversation history
3. Retrieved references
4. Tool outputs
5. The current user message
6. The model's current answer generation

All of these compete for the same limited space.

4. Example Window Sizes

Model	Context window	Rough intuition
GPT-3 (2022)	~4K tokens	a few pages
GPT-3.5	16K tokens	a long article
GPT-4 Turbo	128K tokens	a short book
Claude 3.5	200K tokens	multiple long documents
Gemini 1.5 Pro	1M+ tokens	a very large corpus

5. Key Insight: Bigger Is Not Always Better

A larger window often helps with longer conversations and longer documents, but it also brings tradeoffs:

• higher cost
• heavier computation
• more noise
• weaker use of information in the middle of long contexts

6. Intuitive Analogies

Analogy	Meaning
Desk	how much material can be open at once
Working memory	how much can be actively held
RAM	active runtime information
Spotlight	only what gets attention is truly used well

7. Business Applications

Scenario	Why context matters
Customer support	remembers the current issue and prior constraints
Document analysis	handles whole contracts or reports
Long-form writing	keeps style and consistency
Code review	sees more of the codebase at once

8. What You Need to Remember

• Context is what the model can actually see
• Context Window is how much it can see
• many bad answers are not model problems but context-design problems

9. Recommended Reading

• IBM: https://www.ibm.com/think/topics/context-window
• Zhihu explainer: https://zhuanlan.zhihu.com/p/15530206889
• Context length vs context window: https://www.53ai.com/news/LargeLanguageModel/2024073165281.html
• AI Bot encyclopedia: https://ai-bot.cn/what-is-context-window/