To borrow a sentence from Wikipedia (as it's just slightly more direct than the Conservancy homepage): "Software Freedom Conservancy is an organization that provides a non-profit home and infrastructure support, including legal services, for free/open source software projects." So, to grossly over-simplify: The purpose of Conservancy is to provide for other Free-software projects what the FSF provides for GNU. Most famously, Conservancy has enforced the GPL for BusyBox (a member project of Conservancy), and the Linux kernel (not a member project, but is special in that many contributors have assigned their copyright to Conservancy, and other contributors have authorized Conservancy to represent their copyright).

(It's more accurate to say that SF Conservancy is an offshoot of the Software Freedom Law Center than it is of the FSF.)

As for disagreement with the FSF and "principles of software freedom": Conservancy's principles are Stallman's four freedoms. They aren't "pushing" "ethical licensing"; they hosted a conference that had several talks about it; just as LibrePlanet, the FSF-hosted conference, has also had talks exploring formulations of software ethics that differ from the four freedoms. Indeed, the linked page calls out that so-called "ethical licensing" is non-Free, and advocates for "ethical employment contracts" instead. Any substantive disagreement between Conservancy and the FSF must be fairly recent: Until late-2019 the president of the SF Conservancy was also a member of the FSF's board of directors.