Employers can provide two different types of pension arrangement. They may set up an “occupational pension scheme” which will be managed by a board of trustees. Or they may make an arrangement with a pension provider such as an insurance company to provide a “group personal pension” or a “group stakeholder pension”.
A group personal pension or group stakeholder pension will always be a "money purchase" pension - often called "defined contribution" or "DC", which is very similar to any other type of savings arrangement. An occupational pension scheme may either be a money purchase arrangement, or (though these are now uncommon in most of the private sector) a salary-related pension - often called "defined benefit" or DB. There is more information about both on this site, or you can download a useful guide to pensions from the Money Advice Service.