There is no specific meaning to a specific thread ID because a thread is just a line of activity that is part of a process.
Imagine a process like "quality control". A thread would be a specific "qualitiy control inspector" with an identification number. But they are all doing the same.
In more technical words:
A proccess is an entity of your operating system.
- Exetutable program, that defines code and global data
- has a prive address space
- Code and data are accessable via this address space
- Set of resources (opened files/objects)
- Set of threads
A thread is a line of activity within a process.
- processor context (register contents etc.)
- Stack (usually two separated, one for user and one for kernel mode)
- small private data range
- Threads of a process use the processes address space and resources.
Example:
If you request a web page from the w3wp process it will "summon" a thread and let it do the work of processing your request that finally will deliver you the page.
I hope ths helps you unterstanding TID