The official announcement
Basically, the Squad Cost Rules (SCR) will require clubs to not spend more than 85% of their revenues on transfers + wages. The Top to Bottom Anchoring (TBA) rules require that the clubs' football costs (more than just transfers & wages, I presume) not exceed an undisclosed multiple of the lowest distributed amount to a PL side (e.g. Sheffield United getting the lowest distributed amount from the PL this year). Note that these rules won't be strongly enforced; they'll act more as guidance for the teams on top of the existing PSR rules that are still fully enforced. As part of the trial, if any club breaches the SCR and TBA restrictions, they won't get in trouble unless they go way too far.