So I heard this term in a video recently and never heard it before. I am curious as to what it is in relation to cyber security. The video I was watching was touching on DDoS at the time so I would imagine it has something to do with those sorts of attacks?
The simple way of explaining what it is - is a network of compromised computers or devices that are controlled remotely by an attacker to perform malicious activities, such as sending spam or launching DDoS attacks. It can be within a range of the attack, i.e. close by, or in another country.
Most people use these for DDoS attacks or spam attacks as mentioned. They tend to use several computers although tablets and phones can be used as well.