The second is the information the frame carries, namely time slots. Think of those slots as freight. These slots, in turn, carry a sliced up part of a multiplexed conversation. These help keep the data stream's integrity, making sure that all the frames or digital boxcars keep in order. The slots themselves hold individual call information within the frame, that is, the multiplexed pieces of each conversation as well as signaling and control data.
Slots hold the bits that make up the call.
Certain bits within the slots perform error correction, making sure sure that what you send is what is received. Same way with data sent in frames on telephone land lines. The TDMA based IS-136 uses two slots out of a possible six. Now let's refer to specific time slots. Slots so designated are called channels, ones that do certain jobs.