Tokens are used in OpenAI pricing.

When you make a request to the OpenAI API, they parse your prompt and counts the tokens.

• 1 token ~= 4 chars in English
• 1 token ~= ¾ words
• 100 tokens ~= 75 words

Or

• 1-2 sentence ~= 30 tokens
• 1 paragraph ~= 100 tokens
• 1,500 words ~= 2048 tokens

The OpenAI pricing considers tokens in both the request and the response.