Typographic Symbols

Kramdown converts ', ", <<, >>, ..., --, and --- into their equivalent typographic symbols:

Single quotes (') become ‘fancy quotes’
Double quotes (") also become “fancy quotes”
Fancy quotes can be disabled by escaping the quotes using \: 'non-fancy single quotes', "non-fancy double quotes".
<< and >> become a guillemets, «like this».

Guillements are used as quotation marks in some languages (Esperanto, French, Greek, Italian, Spanish, …).
... becomes an ellipsis, like this: …

Ellipses are used to show when something has been left out, for example when you’ve omitted some words from a quote:

Hamlet asked whether it was “nobler … to suffer the slings and arrows of outrageous fortune or to take arms against a sea of troubles.” Grammarly

Dashes

A single - is just a hyphen, it doesn’t get converted. Hyphens are used for compound words like well-being or advanced-level.
-- becomes an en-dash, which is slightly longer than a normal hyphen, like this: –.

En-dashes are used to indicate spans of time or ranges of numbers: July 9–August 17, or pp. 37–59.

You can also combine words using en-dashes to indicate conflict, connection or direction:

The liberal–conservative debate never ends.
The Perth–Dubai–⁠Boston flight takes more than a day.
There is a north–⁠south railway in the same area as the highway that run east–west.
© 2019 thepunctuationguide.com

You shouldn’t put spaces before or after en-dashes.
--- becomes an em-dash, which is longer again than an em-dash, like this: —

Em-dashes create a strong break in the structure of a sentence, more emphatic than a comma or colon, and drawing attention to the information rather than suggesting that the information is unnecessary like parentheses do. For example:

We bought pencils, rulers, notebook paper, pens, and folders—all of which were on sale, of course—for our clients to use in the courtroom. Get It Write

You can also use just one em-dash, instead of opening and closing ones, if the contained text is at the end of the sentence:

After months of deliberation, the jurors reached a unanimous verdict—guilty. © 2019 thepunctuationguide.com

Another use for em-dashes is when you can’t use a comma to separate a parts of a sentence because the parts themselves contains commas:

After a split second of hesitation, the second baseman leaped for the ball—or, rather, limped for it. Grammarly

You shouldn’t put spaces before or after em-dashes.

Em-dashes can also be used to indicate missing parts of a word:

Mr. J— — testified that the defendant yelled, “Die, a——,” before pulling the trigger. © 2019 thepunctuationguide.com