A UserForm is a Class module provided by VBA. In the VBA IDE in Excel, if you right click on the Project Explorer window and hover your mouse over Insert, you can add a UserForm to your Excel VBA Project. Whan you add a UserForm object, it shows up in the object browser as a Private Class in the VBA Project referenced by your Excel file. A VBA.UserForm is a lot like an Access.Form, but a UserForm can't be bound to data and doesn't have a RecordSource property.
Access is actually a weird amalgam of object models. Access itself only really provides Form and Report objects, and the controls you can put on them. The Database is provided by Jet, and usually people use DAO to read and write to and from Jet tables, but it's DAO that provides the TabelDef, QueryDef, and Recordset objects we're familliar with. And CurrentDb is Access exposing a DAO.Database. File dialogs are from the Office object model. And all programming modules are provided by VBA.
When you look at the navigation pane and see all your tables and queries, forms and reports, it's actually amazing the diverse programming chunks that make that possible, and make it look like one product.
But yeah, UserForm is VBA. DoCmd and Form are Access.