Threads in Processes

Threads are in process, they use the same address space of the process.

How to see threads inside process:
Linux: pstree
UNix : ptree

In general:
AIX : ps -mo THREAD -L pid
Linux : ps -L pid

Topas : press H

Manually, just go to : /proc/pid/lwp/threadsID

What can you do:
Linux : renice integerTID (TID = thread ID)
AIX : you can see which processor handle the threads and define which you want, detail:
http://www.ibm.com/developerworks/aix/library/au-aixprocesscontrol/index.html

Can you kill TID in runtime:
Yes, just kill TID, but not suggested, better to kill the process.
In one well-known application, kill a TID same like killing the whole process.
In the programming there is function to stop only thread though, do googling for it.