What exactly is a training split? How does it work?

For example, if I say ';I work out four days a week with a 3-4 day split';, what exactly does that mean?What exactly is a training split? How does it work?
It's splitting the ammount of days over the course of a week that you will be able to workout during a seven day period.





The three-four split is three days working out and four rest days. Usually done as Mon, Wed and Fri are the training days and Tue, Thur and the weekend ar the rest days.