Thread and a process concepts are different between user-mode debugging and kernel-mode debugging.
In user-mode debugging, a process is an operating system process and a thread is an operating system thread.
In kernel-mode debugging, the debugger engine creates a virtual process for each target; this process represents the kernel and does not correspond to any operating system process. For each physical processor in the target computer, the debugger creates a virtual thread; these threads represent the processors and do not correspond to any operating system threads.
When an event occurs, the engine sets the event process and event thread to the process and thread (operating system or virtual) in which the event occurred.
The current thread is the thread (operating system or virtual) that the engine is currently controlling. The current process is the process (operating system or virtual) that the engine is currently controlling. When an event occurs, the current thread and process are initially set to the event thread and process; but, they can be changed using the clients while the session is accessible.
In kernel mode, the debugger keeps track of an implicit process and implicit thread. The implicit process is the operating system process that determines the translation from virtual to physical memory addresses.
The implicit thread is the operating system thread that determines the target's registers, including call stack, stack frame, and instruction offset.
When an event occurs, the implicit thread and implicit process are initially set to the event thread and process; they can be changed while the session is accessible.
Thread and Process Data
The engine maintains several pieces of information about each thread and process. This includes the system thread and process ID and system handles, and the process environment (PEB), the thread environment block (TEB), and their locations in target's memory.
For details about using thread and processes, see Controlling Threads and Processes.