Do I have to use ETH on Uniswap?

Sure, here's a description that simulates the tone of a questioner: "Hey there, I'm curious about Uniswap and how it works. One thing I've been wondering is, do I have to use ETH specifically on Uniswap? Or can I use other cryptocurrencies to trade on the platform? I'm still pretty new to the world of decentralized exchanges, so I'm trying to get a better understanding of the basics. Thanks in advance for any insight you can provide!