How are Siebel server components used?

I have a very naïve question around how server components are used in Siebel. My understanding is anything done on UI context is processed by Object Manager. But when exactly are components like workflow process manager and EAI Object manager used? I am asking these question because I need to work on suggesting parameter changes to tune the components but before that I want to understand when exactly are components used. To make it clear lets take below examples/questions:

1. If I have deployed a workflow on server which is called behind click of a button will this workflow be processed by Object manager as it is invoked in UI context or in general all workflows use Workflow process manager component?