Do I need to pay to use OpenAI API?

I'm curious about the OpenAI API and its usage costs. As someone interested in leveraging this technology for my projects, I'd like to know if there are any fees associated with using the OpenAI API. Do I need to pay to access and utilize its features, or is there a free tier available for basic usage? If there are costs involved, how do they scale with increased usage? I'm eager to learn more about the financial aspect of working with OpenAI's API.