A lip scrub contains exfoliate and emollient components - removing dry skin with sugar’s slightly rough texture, and leaving your lips soft and moisturized with its butters or oils. 

When you are looking for a good lip scrub, try looking for following ingredients that are commonly found:

• Emollients: coconut oil, Shea butter, avocado oil, coconut butter, grape seed oil, jojoba oil, pure Vitamin E oil, etc. 
• Exfoliates: brown cane sugar, pure sugar crystals, coffee grounds, coarse oats, etc.