This command specifies the threads on which subsequent commands to the debugger will operate.
context all context thread-selectors [...]
Where syntax element thread-selectors specifies a string that selects one or more UDF threads being debugged.
You can specify one or more specific threads, or all threads to include all currently active threads. When the context contains multiple threads, commands operate on all of them serially. The output for each thread contains a line that identifies the thread followed by a line of command-related information. After a breakpoint or other exception stops a thread, the context defaults to that thread making it the current context.