When we add spaces around a hyphen, it becomes a dash - and it's used to introduce afterthoughts or side-comments.

I think you are talking about the - (hyphen). It can be used in different ways. We hyphenate two words if they are adjectives and when they act as one word and help a noun; for example, the hard-working man or the man-eating tiger (these are called compound adjectives). Another example of when you use a hyphen is with numbers for example: Hours of work: 8am-5pm Second world war was from 1939-1945 Hope that helps.

No no, I didn't explain myself, I would like to know the use on dash. Cause in italian we use quotation like in Italian but also to identify exactly the word between...

to mark the beginning and end of direct speech (i.e. a speaker’s words written down exactly as they were spoken): ‘That,’ he said, ‘is nonsense.’ ‘What time will he arrive?’ she asked.

quotation marks ? - when something that has been said by someone is repeated, either as part of a narrative, or when referring to what has been said.