Masterfile +3 is an updated, discified version of one of the most popular database packages for the Spectrum. It works on the same sort of principles as other databases: you can define the sort of information held in each file (up to 60 "fields" per record) enter huge amounts of information (for instance, a thousand names and addresses with up to 254 characters in each), and sort through the info in various useful ways.
Boxes and panels of any colour can be added to the files to create labels, index cards and tables, and you can even perform calculations within records using spreadsheet-like formulae.
The program's totally menu-driven, so even a duffer can use it to create, for instance, address lists, collection files, stock control routines, price lists, club records and so on. Just the sort of thing the Plus 3 was designed for.