"They could multitask, but it wasn’t modern pre-emptive multitasking. Instead, the applications cooperated rather than the operating system being able to hand out resources. This meant a poorly behaved program could do a lot more to gum up the works in 1994 than it can do today, since the operating system just had to trust all of the programs to cooperate fairly."

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The importance of this should not be understated.

Under Windows 3.1, or MacOS, programs could be written to periodically hand control back to the OS, allowing the OS to then hand-off control to another program, thus allowing cooperative multi-tasking. However, every single program involved had to be written to do this. If you ran a program that was older or not written for multi-tasking, it'd assume complete control of your machine until it terminated. Even multi-tasking friendly programs would hang your machine if they went into an infinite loop. There was no hope of appeal to the almighty task manager! The result was Windows (and MacOS prior to OS X) were simply not very good at multi-tasking, so users mostly didn't do it.

Preemptive multi-tasking allowed the OS to forcibly take back control from programs. Programs would be given slices of CPU time and didn't have to worry about handing control back, because the OS would simply take it back. If a program went into an infinite loop, it would continue getting slices of the CPU's attention, but so too would other programs and the OS itself. This meant you could Alt-Tab out of a word processor to look up something in your web browser without the risk of a browser crash bringing down your computer and causing you to lose everything you'd written since you last saved.

Windows 95 put an end (mostly) to the punishment of multi-tasking and changed how typical desktop users used their computers.