Lemmy is similar to sites like Reddit, Lobste.rs, or Hacker News: you subscribe to forums you\’re interested in, post links and discussions, then vote, and comment on them. Behind the scenes, it is very different; anyone can easily run a server, and all these servers are federated (think email), and connected to the same universe, called the Fediverse. For a link aggregator, this means a user registered on one server can subscribe to forums on any other server, and can have discussions with users registered elsewhere. The overall goal is to create an easily self-hostable, decentralized alternative to Reddit and other link aggregators, outside of their corporate control and meddling.
They don’t seem to filtered specifically if they are trade-free, but both of the servers are, since there are no trackers, ads or anything else.