A "communication path" created by dividing a radio channel in time.
Since traffic on the discreet channel is divided in time more calls can be made simultaneously. This results in more efficient utilization of the discreet channel and increases the capacity by making more "communication paths" available.
The split in time also enables full duplex calls, i.e. telephone calls. This is made possible by using everyother time slot for transmission and receiving.
Also see the image to the right - TDMA > Time Divisions Multiple Access.