Terminology

channel
A group of containers, used to pass data between programs. A channel is analogous to a parameter list.
container
A named block of data used to pass information between programs. You can think of it as a “named communication area (COMMAREA)”. Programs can pass any number of containers between each other. Containers are grouped together in sets called channels.
current channel
The channel, if any, with which a program is invoked. The current channel, for a particular invocation of a particular program, does not change.