meaning of sintaxis: var=$'value' ?

What is the efect to use the syntax like that:

var=$'value'

The result seems the same as

var=value

I was compare the result of 'env' and 'typeset' and I see that the same variable in 'env' presented as var=value, but in 'typeset' the same vars with the same value presented with $'..'.
What is that and why?

Is there any benefit to use that syntaxis?

I still have no any resolution on this question.
Does anybody has any idea regarding that syntaxis?

What shell are you using ?
With bash, the display is in the form var='value' not var=$'value'

From bash man pages :

Jean-Pierre.