The basic jist of it is to make crypto and security a usable experience on the desktop. This means laying down a foundation for integrating crypto into applications easily. We have tons of technically excellent crypto libraries and security components, but there hasn’t been the glue to tie them together and make them usable in apps.
It’s sort of like what PackageKit or NetworkManager did for their respective areas. Linux (and other open source OS’s are) really great at networking, but NetworkManager pulled together all the various bits, and completed missing parts to make it to be usable.