An unpatched software is any software that is not up to date, causing it to be more susceptible to attacks.
Up to Date?
The threat of unmatched software is real. For example, a single unpatched copy of Microsoft Outlook led to the July 2018 compromise of 1.5 million health records, including that of the prime minister of Singapore.
How do you Combat It?
One can easily prevent unmatched software by regularly updating software and keep automatic updates for all softwares. This will give one's devices immune to many cyber attacks.
This equipment is getting old, but I don't feel like getting a new one...
The next day...
Ow! I got hurt on the treadmill!
Yay! I'm all better and safer with this new equipment!
John here is not fixing his old equipment. This will make him more prone to injuries.
Since the equipment was outdated, John was more prone to injuries. This is just like how a computer is more prone to malwares with unmatched software.
Since John got new, up-to-date machines, he will be safer and less likely to get injured.