1. How to understand Workflo?

WorkFlow in simple: The state of an object changes from one
state to anather with Human activity.
There must Human Activity involved.
Example from agent to operational manager to next higher

Agents submits a paper to be approved by his operational
Agents object state is being changed by his operation
manager with some interface/GUI etc.

2. What kind of information goes to Technical Specification for SAP Business workfllows?

While developing the workflows, one has to make use of
interface, methods, data types , reference types etc. The
technical specification should carry about the changes made
in interface, methods, datatypes, etc.