Can players trade Aniimo?

Trading is tied to a place. Both of you have to be standing in one of the shared social areas for it to happen, so it is something you arrange and travel to rather than something you do on the spot wherever you happen to be in the field.

Those shared areas are where you run into other players in the first place, along with their trailers: open-world settlements and RV campsites are public hubs, and RV parks are the designated version of that. In an RV park you park alongside other people, visit their RVs, rest, and decorate camping platforms. If you want to trade with a specific person, the practical move is to agree on one of these spots and meet there.

What else the shared areas are for

Trading sits inside the online cooperative side of the game rather than off on its own. The same multiplayer layer lets you team up to explore the open world, take on boss battles, and handle alpha encounters together, so a meet-up to swap creatures can easily turn into a group heading out to fight something.

The game also has PvP modes where players battle each other directly. That is separate from trading, but it means the players you meet in a hub are potential opponents as well as potential trade partners.

Not settled: What restrictions apply to a trade, such as whether every Aniimo is tradeable or whether a swap can be reversed, is not settled yet.