Dialplan Switch Statements
The switch statement permits a server to share the dialplan with another server. To understand when a switch would be searched for dialplan extensions you should read the Contexts, Extensions, and Priorities section as it covers Dialplan search order.
Basic switch statement
As an example, with remote IAX switching you get transparent access to the remote Asterisk PBX.
The lswitch statement
An "lswitch" is like a switch but is literal, in that variable substitution is not performed at load time but is passed to the switch directly (presumably to be substituted in the switch routine itself)
The eswitch statement
An "eswitch" is like a switch but the evaluation of variable substitution is performed at runtime before being passed to the switch routine.