What is the Uniswap fee?

Could you please clarify for me what the Uniswap fee entails? As a user of the platform, I'm curious about the specific costs associated with trading on Uniswap. Is it a flat rate, or does it vary based on certain factors? Additionally, is there a way to minimize or optimize these fees to ensure a more cost-effective trading experience? Understanding the ins and outs of the Uniswap fee structure is crucial for me to make informed decisions as a crypto investor.