A lot of people use Gmail. It's great, but having to access it via a web browser instead of a dedicated program can sometimes be inconvenient. Browsers take up lots of RAM, for example. And it's annoyingly easy to inadvertently close your mail when closing your browser, even if you didn't really mean to close the Gmail tab. Plus, because you're accessing Gmail via a browser, there's no Gmail icon on your task bar. It's just another browser window or tab. So it's not easy to quickly flip between your email and another open program.
Kiwi for Gmail is an email program designed solely for Gmail. It works like a normal Windows program rather than a web browser, but the experience is precisely the same. You will hardly know you're not using a browser. Plus, you don't need to configure Gmail settings for IMAP or POP in order to use it. Just log into Gmail via Kiwi in the normal way.