Some of the software on my Mac is behaving erratically, unlike the way it worked after it was installed. Someone suggested that I zap ?� the computer; what are they talking about?

If software on your Mac is behaving erratically (either the operating system or specific applications), you may be able to quickly solve the issue by "zapping" the memory on your Mac.
NVRAM (nonvolatile random-access memory) is a small amount of memory that your Mac uses to store certain settings and access them quickly. PRAM (Parameter RAM) stores similar information, and the steps for resetting NVRAM and PRAM are the same. To "zap," shut down your Mac, then turn it on and immediately press and hold these four keys together: Option, Command, P, and R. Release the keys after about 20 seconds (after you hear two reboot bongs from your operating system) and allow your Mac to start normally.