Push-up bras do exactly what they say, they push your breasts up and together to give maximum cleavage. They are usually plunge bras as well, this means the cups join low between the breasts so you can wear something low to show them off. They are padded so your breasts can appear a couple of cup sizes larger than they are. They are great if your breasts are smaller and you want to draw attention to them and make them look bigger.
Some will have removable padding or inserts, in other ones the padding will be built in. Some even contain gel padding that will mould to your shape and give the look and feel of real breasts. If you already have full breasts and want the look of a push-up bra but don’t want to add any extra size look for ones where the padding is removable. See padded bras for more information about padding.