basic doubt on ferrite core's working

I have heard that ferrites are used in transformers and other applications. And that they are used for concentrating flux. Is this right? What property helps them do this? What is the relation between that property and the magnetic flux? Can you kindly provide me the answer and if possible a document which can explain in easy terms, why ferrites are able to concentrate flux?

So if I simulate a structure with air core and ferrite core, if my assumption is right, flux would be more in the ferrite core right? Can I mathematically write an equation which can say, the amount of flux at some point outside and inside the core? If so, how can I go about in calculating that value?

thanks and regards,

I have a few years experience using ferrite cores. In my industry we use them to suppress energy or charges that may travel across a conducting cable and get into other portions of the systems that are sensitive to such charge. So they pretty much behave as a attenuator or a frequency dependent resin the simplest terms.

Look for any company website that make ferrite material. They should have tutorials on techniques of suppression. Like this company has.
http://www.elmac.co.uk/pdfs/ferrite.pdf