Most HP printer files contain drivers for a family of printers, i.e. Laserjet 4, 4+, 4P. Some will contain drivers for both 32-bit and 64-bit versions of Windows.
Virtually all HP printers come with at least three drivers: PCL5e, PCL6, and Postscript. Each of these uses different command sequences to control the printer, and has slightly different capabilities. Choose the 5e for the most basic (and usually reliable) driver; PCL6 for advanced features (also sometimes necessary for increased resolution printing); Postscript for best compatibility with a range of programs that use mixed printing modes, such as Adobe products.
Which works "best" will depend on the programs you run and the model of printer. In general, PCL5e is the most reliable and PCL6 works properly with the widest range of programs.
And going against all this, HP is moving mostly to a "Universal" driver that will work for multiple printers installed.