There is widespread confusion about when prosecutorial discretion applies, what it is, and when would it actually help someone facing removal.
First, prosecutorial discretion is not new. It has always been there, the only thing new is some additional guidance about when to use it. The agents of Immigration – USCIS/ICE/CBP have always had discretion on certain issues and could decide whether or not to prosecute (charge/pursue) certain deportations. Prosecutorial Discretion as a measure of relief is basically a request that the Dept of Homeland Security/ICE administratively close proceedings (ie halt the removal) of someone who is not a criminal alien and has very sympathetic factors. It does not grant you legal status nor does it currently grant work permits.
It is helpful to look at the actual memo that guides the courts regarding when Prosecutorial Discretion may be applied in the favor of the alien.
When you are facing the possibility of deportation, make sure your attorney makes a back-up case for prosecutorial discretion as well.
People with criminal history, including DUIs, thefts, etc. are less likely to receive the benefit of prosecutorial discretion.