There is so many different lubes that you can get! There are many of them out there from many different companies and causes different things to happen.
There are some for sensitive people, people whose allergic to certain things, Anal, There is eatable, lick able ones there is ones that dries quickly then there is ones doesn't dry as quickly. There is ones that stays wets for hours also synthetic ones that feels real. There are flavored one and just all kinds of them including warming ones that get really warm with every motion.
Lubes help so it doesn't hurt. Lube lets you just slide on penises and toys and even tampons with no problem. It helps when you can't get wet on your own and your ready.