What does maintenance cover in a software license?

We are negotiating is a description license to Enterprise software. The agreement includes both of the license and support for the product. The vendor defines support to include maintenance releases. However, it is not clear what is included in the maintenance release. The agreement references point versions but the determination of whether a release is a point version or a major release seems arbitrary.

Speaking only as a software developer, the terms are not arbitrary. They might differ from product-to-product or among companies. But if the software or web development company is worth anything, then versioning has precise meaning. You should probably ask them for their versioning practices. You could also ask for release notes from prior version of each release type - x.y.z - where x, y, and z are all different version types.