I had a discussion with some people today on hyphen and dashes. They had concluded that hyphen, which is used to link two connecting words (book-bag) is the longer line – instead of the shorter line -, and that the shorter line is for the dash, which is used to continue an argument/show something within a passage. 

Is this true? Is there really a difference between the line length in the hyphen and dash symbols? I had always thought that they were of the same length. 

Supposedly:

* Hyphen : –
* Dash.... : -

(Dots used to space out to show the difference in length.)