"Side-by-side installation" refers to two separate installation runs that share the same AppId setting (or if AppId is not set, the same AppName setting) but not the other "Same application" requirements. Two of such installation runs will usually lead to two actual installations of the files. To avoid entries with identical names in the Add/Remove Programs Control Panel applet Setup will automatically mark the new entry with a text like "Current user" or "64-bit" when necessary during a side-by-side installation.