Cerazette is a mini pill, or progesterone only pill. The main ingredient in Cerazette is a synthetic hormone called desogestrel. It was the first brand of desogestrel pill available, so it's got a long track record for safety. It doesn’t contain any oestrogen, like the combined pill, which means it can be used by women who are breastfeeding.
A lot of women who take Cerazette will have no periods or very infrequent, light bleeding which is why many women prefer it. But it may not have some of the secondary benefits associated with the combined pill, such as helping with oily skin or hair.