Yes, out of the box Access databases are multi-user.
Note, though, that it's strongly recommended that you split your application
into a front-end (containing the queries, forms, reports, macros and
modules) and a back-end (containing just the tables). Only the back-end
should be on the server: each user should have his/her own copy of the
front-end, preferably on their hard drive. This significantly reduces the
risk of database corruption.
Note that each user will need to have Read, Write, eXecute and Delete
permissions on the folder where the back-end database resides. This is
because a locking file (.LDB) is created there when the first user connects
to the database, the locking file is updated by subsequent users, and
deleted when the last user releases the database.
There's a built-in splitter wizard in all versions of Access, although it's
fairly simple to do manually. See what Tony Toews has at
http://www.granite.ab.ca/access/splitapp/index.htm