Not Bitcoin, but another crypto currency which connects to Bitcoin via "bridges".

I don't really know this liquid but I guess the process is similar to:

You send bitcoin to a bitcoin wallet and receive a token on the liquid sidechain which represents your bitcoin. This liquid token is cheaper to transfer. Then at some point you want to swap out, so you send your liquid token to some wallet, and those liquid tokens are destroyed, and you receive the amount of bitcoin they represent into a wallet you control.

Found this if you're more interested. I don't know, I'm automatically not a fan of sidechains.