What is Bitcoin (BTC) profit calculator?

Could you elaborate on what a Bitcoin (BTC) profit calculator is? I'm curious to understand how it works and how it can assist investors in estimating their potential earnings. Specifically, I'm interested in knowing if it considers factors such as the current market price, investment amount, transaction fees, and potential future price fluctuations. Additionally, I'd like to know if it's a reliable tool for making informed investment decisions or if it's merely a rough estimation. Could you provide a brief description of how the calculator functions and what it aims to achieve?