Breast implants can be smooth or textured (rough).
Textured surfaces are more commonly used on teardrop shaped implants than on round implants.
This is to help keep the teardrop implant in place (a round shaped implant rotating is not a problem, however, a teardrop implant should move.
Round implants tend to stay in place more easily and do not benefit as much from a textured surface.
The other reason why some implants are textured is that they were found to potentially lower the risk of capsular contracture when the implant is being placed in front of the muscle (sub-glandular pocket), rather than behind the muscle.
However, studies showed that when the implant is placed behind the muscle (which is the most common method) there is little if any difference in the risk of capsular contraction over using smooth implants.
Textured implants generally have a higher complication rate.
Your surgeon will recommend the best implant size, shape and texture for your body, and to achieve the look you want.