An em dash has the width of a m and is used primarily as a parentheses or when there is a break in thought.
eg: You guessed it right—he won the elections.
To get an em dash in MS-Word (laptop users), type 2 hyphens without any space. Also there should be no space between the first word and the second word ( ‘right’ and ‘he’ in the above example). MS-Word automatically picks it up as an em-dash.
The em dash is also available as a symbol in MS-Word (Insert>Symbol).
An en-dash has the width of a n and is used primarily to denote a range (as a replacement for ‘to’).
The en dash is available as a symbol in MS-Word (Insert>Symbol).
The hyphen is smaller in size than the em dash and the en dash and is used to link words or parts of words. It is primarily used to join compound words, prefixes to words and to show word breaks.
The hyphen is available as a key on the keyboard.
Note: It is recommended not to use any space before or after the em dash, en dash or hyphen.