Fields of Interest , helps you to determine whether the foundation is likely to be interested in the type of project you have in mind. If the foundation's field of interest is Higher Education, and you need to fund an elementary school project, you can skip that foundation. Foundations hate to receive grant applications that are unrelated to their fields of interest, so pay attention to this section. Types of Support , tells you what types of grants the foundation is willing to fund. Some foundations only support building projects, some support only scholarships, some support only research, some only conferences, etc.
Many foundations support more than one type of project, but few support everything under the sun.
Foundations hate to receive grant applications for types of projects that they do not support, so, again, pay attention. Limitations , gives you absolute things the foundation will not do. Most of the limitations are geographic in nature. Many foundations give only in specified geographical regions. If you aren't within that region, you can quickly move on to the next possibility.