I'm not 100% sure if this is what you're referring to because they like to change names of stuff (and I haven't dealt with projects for a while), but at one point there was kind of a "basic" projects module and an Advanced version.
Basic projects are not technically their own record, they're basically just subcustomers and they don't allow a ton of functionality beyond tagging transactions and rev rec, etc
Where the Advanced Projects is more of a full project suite where you can do all the fancy stuff outlined in this PDF. My guess is that might be the difference between the two products you're mentioning.