Start Process

Those are back end architecture of Appian . Appian Engines You want to know more about it go through this link,i suggest you to don't dive too deep into that this early.

These engines work is to store , retrieve real time data.And in general Analytics (which are useful for you to create reports ) & process execution engines comes in pairs.

what is the differance between asynchronous subprocess and start process

Hello JPotharaju 

I hope this will make you understand.

Comparing ways to start a process from a process

This shows the differences between Synchronous, Asynchronous and Start Process.

 Asynchronous Sub-Process vs Start Process Smart Service 

Have a look into the above thread.And go though the link Chaitanya provided.

Start Subprocess: Fire and forget - starts another process in the background without waiting for it to finish.
Async Process: More control - starts another process asynchronously but allows some monitoring and potential data retrieval after it's done.

Choosing Between Them:
If your main process doesn't depend on the subprocess and you don't need return data, use an start process for simplicity.
If some level of communication or control over the Async subprocess is necessary, consider using Start Process.

Start Subprocess: Fire and forget - starts another process in the background without waiting for it to finish.
Async Process: More control - starts another process asynchronously but allows some monitoring and potential data retrieval after it's done.

Choosing Between Them:
If your main process doesn't depend on the subprocess and you don't need return data, use an start process for simplicity.
If some level of communication or control over the Async subprocess is necessary, consider using Start Process.

Shubham Aware said:

Async Subprocess: Fire and forget - starts another process in the background without waiting for it to finish.
Start Process: More control - starts another process asynchronously but allows some monitoring and potential data retrieval after it's done.

I think it's opposite. In Async Subprocess we can maintain relationship and we can pass data by reference

Yes correct! Thanks
I edited my reply.