a lipstain unlike lipsticks/glosses/ balms etc tints your lips and gives colour to your lips in the result that the colour will blend into your lips making them look totally natural. its sort of like a lip "dye" instead lip "paint". they are thinner in their consistency compared to l/s and l/g's and act like a dye to your lips making them coloured (to whatever the stain's colour is) but making them appear like that is their natural colour.
hope you got what i was trying to say. if anything was unclear, dont hesitate to ask and i'll try to explain it better!
HTH!
