What is the difference between antivirus and anti spyware software (high level)?

A common misconception is that Macs/Apples are free or have a low threshold of infection – did you know that in 1982 by Richard Skrenta, it attached itself to the Apple DOS 3.3 operating system and spread by floppy disk This virus was originally a joke, created by a high school student and put onto a game on floppy disk. On its 50th use the Elk Cloner virus would be activated, infecting the computer and displaying a short poem beginning "Elk Cloner: The program with a personality".

Spyware Software is malicious software or code that tracks and reports what you do and can by its nature put a load on your system or a footprint that bogs down your system while reporting back to some third person information about you. This information can be as simple as your browser settings and screen resolution or as detailed as your email, files on your computer or any keystroke thus any transaction including financial that you do on a system.

ViralVirus Software is intended to corrupt your system in some way either by slowing down your software processes or destroying data.

Bottom line is both are bad as such you should have either a combination program that covers both but the ideal scenario are two programs tasked to specifically deal with each unique threat to the integrity of your operating system or data working in tandem but separate from the other.

Anti spyware software looks for any errant program or data that behaves in such a way that indicates it may be sending data to a remote person and removes it.

Anti virus software looks for any errant program or data that may corrupt your software and the integrity of your operating system and works to either isolate or remove it.

On the surface they seem like they are the same and to some extend you are right because there is some minor overlap. That aside these products serve two different purposes. Both do this using heuristics (educated guesses and/or intuitive judgments ) and both typically depends on constant information updates from the author of the programs to keep track of new threats.