How to understand class dependency diagram?

Question

OOP

Please help to describe in words what is observed in the class interaction diagram, with a code example.

I see only two types of relationships - inheritance, implementation.

Implementation, this means an object of a particular class is created and used in another class through injection? Or through direct composition?

Can you describe this scheme with a code example?
For example, which class do we initialize first? As I correctly understand from the diagram, there are two classes to choose from for initializing the Envirement, the ready instance of which is passed to the Command class, and how does it, in turn, decide which output method to call?

thanks for the help