― the world was a lot bigger than I had imagined it to be ―

[keannu]

Is this also an emphasis? I mean the dash.
ex)The important lesson I learned at Billups ― the world was a lot bigger than I had imagined it to be ― was a little painful.
It meant I was a lot smaller than I’d realized. I went on to attend a state university and I began to write about my disappearing dreams and new dreams, about wishing and disappointment and feeling small. One day a professor there took hold of me and said, “You’re a writer.” Until then, I hadn’t reall

 

[BobK]

Paired dashes mark a parenthesis. The material introduced parenthetically may provide emphasis; but in this case it doesn't. It just explains what 'the lesson' was.

b

 

[keannu]

I'm trying to practice using punctuation nowdays. When can I use paired dashes for explanation other than emphasis?
Does it depend on a writer's decision?

 

[BobK]

In something like this first example, the dashes mark a parentheisis that is emphatic. In the second example, there is no emphasis -just more information. (Note: even when not paired, a dash needn't signify emphasis; see my last sentence for an example.)

Examples with parenthetical dahses:

• The notice said that everybody - on pain of death - had to go. [Emphasis]
• I used to go - every Monday - to the farm. [No emphasis]

But I'm not the best theorist on punctuation - especially where dashes are involved. ;-) Wait for some other views.

b