Corsets can broadly be divided into underbust and overbust types.
An underbust corset 
An overbust corset
The difference is pretty much about how much of your chest a corset covers. Lots of people find one type more comfortable and/or flattering for them, while others enjoy both equally. Underbust and overbust corsets can also serve quite different purposes.
As you read through the following, it’s worth remembering that any corset can be used to achieve multiple goals, some of which can be completely opposite to each other, depending on the way that it’s cut and constructed (for example, you can design a corset to either emphasize or visually reduce your body curves).
A corset for curves 
A corset for straighter lines
Most traditional and specialty corset styles can be made as either an underbust or overbust, but some styles have to be one or the other.
The Underbust
The top edge of an underbust corset sits right about the place where your chest turns into your abdomen. If you wear bras, the top edge is just about at bra band level.
This style is your best bet if you want the following:
- To maximize lower back support
- To get the greatest amount of waist reduction and hourglass shaping
- To straighten your hip profile and/or waist but don’t want to include your chest
- A corset that’s least likely to show under even lightweight or snug clothing
- To emphasize, not flatten, a small bust
- Have sensitive skin that chafes easily at friction points (especially the underarm area)
Corset Styles – Overbust
The top edge of an overbust corset covers at least some of your chest area. The coverage can vary according to your preferences; it can go high enough to wear as a stand-alone top or stop at the nipples. If you want to a corset that can create a straighter chest profile, replace bra wearing, support larger breasts, or otherwise modify the chest area, you pretty much need an overbust.
Felix & Kitty corsets can usually be customized to accommodate even people who haven’t had success with overbust corsets in the past. For example, because most corsets out there are made for only a small range of cup sizes, people with larger busts often assume that an overbust will shove their chests up to their chin – something that should NEVER happen in a properly fitted corset (unless you wanted it that way!).
Depending on how they’re shaped, overbust corsets can be used when you want:
- Support for your mid-back
- Relief from shoulder or back pain due to the weight of the bust
- Uplift and breast support without a bra, if you normally wear one
- To reduce the curvature of your chest and/or hips and create a straighter profile
- To solidly contain your chest and prevent bouncing during high-impact exercise
- Bust emphasis and enhanced cleavage
- To visually lengthen your torso
