What are the different kinds of birth control pills?

There are two main kinds of birth control pills:

Combination birth control pills come in different mixtures of active and inactive pills, depending on how often you want to have periods:

Combination birth control pills are also categorized according to whether the dose of hormones in the active pills stays the same or varies:

Most combination birth control pills contain 10 to 35 micrograms of ethinyl estradiol, a kind of estrogen. Women who are sensitive to hormones may benefit from taking a pill that contains a dose of estrogen at the lower end of this range. However, low-dose pills may result in more breakthrough bleeding — bleeding or spotting between periods — than higher dose pills.