These are community-led organisations that provide land, homes and other assets to meet the long-term needs of the community. They have a membership structure that is open to anyone who lives or works in the local area, whether or not they live in the properties the trust provides. CLTs deliver things like homes, as well as meeting spaces, workspaces, shops, pubs, farms and gardens. They hold these assets in trust for the benefit of the community and ensure that they remain permanently affordable and provide a long-term income stream.
The National CLT Network provides guidance, funding, toolkits and advice for anyone running or setting up a CLT. Also see CLT structure explanation here. In terms of a suitable legal framework this can vary as long as it meets the defining criteria (ie, an asset lock, open membership to community members and not-for-profit).