What is the Ismaili equivalent of zakah?

In Sunni Islam, there's a concept of *zakah* -- 2.5% (1/40) of your savings saved for a year need to be given to the poor in eight groups, which are outlined in *ayah az-zakah* (The Ayah of Zakah). This is well understood. I know some people who are Ismailis. I have heard them talking about a similar concept, except that it is one eighth (12.5%), and apparently it also applies to cooked food and other things. My question is, **what is this called and what is the "fiqh" of it?**