The dash is a punctuation mark that is similar in appearance to the hyphen and minus sign but differs from these symbols in length and, in some fonts, height above the baseline. Wikipedia
Inserting an em or en dash using Ctrl and keyboard shortcuts. To insert an em dash, click where you want to insert the em dash and then press Ctrl + Alt + – (minus sign on the numeric keypad). To insert an en dash, click where you want to insert the en dash and then press Ctrl + – (minus sign on the numeric keyboard).
A dash is a little horizontal line that floats in the middle of a line of text (not at the bottom: that’s an underscore). It’s longer than a hyphen and is commonly used to indicate a range or a pause. Dashes are used to separate groups of words, not to separate parts of words like a hyphen does.