Is it a basic android system?
I’m not sure what the ‘basic’ refers to exactly, but it’s a Android distribution like LineageOS (and currently Replicant’s development is actually based on LineageOS, formerly on AOSP) and ships with only basic apps like Phone, Contacts, Messaging, etc. The major difference comes with the ethical/politcal approach of Replicant to remove all proprietary parts (e.g. programs, libraries, firmwares) and (trying) to replace them with free software which results in missing GPS, WiFI or limited graphical support for now, depending on the phones hardware.
I am still hoping for open hardware at some point in time.
I think a lot of people are hoping for this very badly too.