Single step one line (step into calls). With multithreaded programs when a method call is stepped over, all threads are implicitly resumed for the duration of that method call in order to avoid deadlock. Non-active threads cannot be stepped.
Single step n lines (step into calls).
Step up and out of the current method.
Step the given thread. Does not apply to step up.
Step the given LWP. Does not implicitly resume all LWPs when stepping over a method.