Rado is a description language to express randomizer logic chains in, and a library (written most likely in Rust) to load and evaluate item placements for item randomizers in games. It's inteded primarily for use in games like metroidvanias and adventure games, where items unlock progression to other items requiring possibly-complex logic for which items can be used to get where, rather than in, say, an RPG with randomized character abilities.
The immediate goal is to write a unified description of randomizer logics so that they can easily be shared across many tools. Probably the most immediate application would be to make it easier to allow trackers to support different logis. The other application is to allow randomizers to be able to outsource the "Is this arrangement of items valid?" portion of the randomization algorithms. That said, there are no immediate plans to provide randomization algorithms directly in the Rado libraries.
The language is named after graph theorist Richard Rado, and in particular the Rado graph which is the graph you almost always get when you try to generate a random infinite graph. It also sounds quite close to "rando".