I heard something about XMRdotTwo (or maybe XMRdotTo?). Can someone explain to me what this is? I heard that you can use it to pay Bitcoin addresses with Monero.
You are probably referring to XMR.to, a website that allows people to make anonymous payments to a Bitcoin address with Monero.
XMR is the trading symbol for Monero, which is why the domain is relevant.
The website has no registration. However, they log your IP address. For extra privacy, the service can be accessed through its onion (Tor) site