Overview
A token is not the same as a word. A practical approximation is that one token represents about 0.7 words, although the exact relationship depends on the text.
Agent models are described with context capacities ranging from hundreds of thousands to approximately one million tokens. A 200,000-token context therefore represents a very large amount of text, but it is still finite.
The raw maximum can be misleading. The user does not begin with the full context window available. System instructions, memory, tools, and skills may consume a significant amount before the first meaningful message is sent.
A large capacity also does not mean that filling the entire window is desirable. The objective is not to maximize token usage. The objective is to give the model the smallest amount of information that is sufficient for high-quality work.