Leave category doubt

Gess> Apply for leave here in the leave category drop down we see Leave without pay as a option also another option as LWP( unable to work) . What is the difference between these 2. I will be returning post ML and have exhausted all other leaves so wish to to take leave without pay for 1 more month. So which option shall I select here. Also during this period will any salary be credited deduction the basic pay.