What is a gate check fee?

Excuse me, could you clarify what a gate check fee entails? I'm curious to know if it's a standard charge for certain airline passengers or if it applies specifically to certain situations. Also, how does one go about paying this fee, and are there any potential ways to avoid it altogether? Lastly, is this fee associated with any particular airline or is it a universal practice in the aviation industry? Thank you for your time and assistance in clarifying this matter.