Enlightenment is man's emergence from his self-incurred immaturity. Immaturity is the inability to use one's own understanding without guidance of another. This immaturity is self-incurred if its cause is not lack of understanding, but lack of resolution and courage to use it without the guidance of another. The motto of enlightenment is therefore: Sapere aude! (54)
Kant holds that only a few individuals will be able to overcome the obstacles to their own enlightenment by themselves. An entire public can become enlightened, however, if they are free to discuss their views, because then the self-enlightened few "will disseminate the spirit of rational respect for personal value and the duty of all men to think for themselves." (55) (It is notable that Kant thinks of this as a duty, and not just a right.) However, in the circumstances of open public discussion, opinion leaders who are not themselves enlightened can also gain influence. From this, Kant concludes the public can only be enlightened slowly, and that revolution may overthrow autocratic government, but only at the cost of compelling adherence to a new set of dogmas.
I think an implied premise is that it takes time for rational criticism, rather than prejudice, to win the public struggle of ideas. Revolution, however, cuts debate short before it reaches its natural equilibrium of enlightenment.
The bulk of the remainder of the essay if given over to distinguishing what Kant calls the public and private uses of reason. By the private use of reason he means what people say while working in an official capacity -- as a judge, a bureaucrat, a military officer, or (and I can imagine this was very important in Kant's Prussia) a minister of the established church. By public use of reason he means what people say to a general public outside of any official capacity. He argues that a ruler should expect people to act accordance with state policy with respect to the private use of reason. But he appeals to rulers to allow free debate outside of official capacities -- free public use of reason. He captures this distinction (more than once) with the slogan "Argue as much as you like and about whatever you like, but obey!" (55, 59).
There are a couple of wrinkles to this. Kant urges rulers to allow congregations to adjust their doctrines to the development of their adherents understanding if the existing doctrines are found wanting after public debate. Kant also holds that a public official who not only disagrees with their orders, but finds them absolutely contrary to reason, has the option to resign.
Kant concludes with a paragraph charting a relationship between intellectual and civil freedom. By intellectual freedom I take it that he means the freedom of public discussion, and by civil freedom I take it that he means the freedom to actually participate in the process of making laws and governing. Kant argues that intellectual freedom should come before civil freedom. He says that permitting civil freedom too early may even endanger intellectual freedom. However, intellectual freedom gradually prepares the public for widespread civil freedom.
How does intellectual freedom supposed to prepare the public for civic participation? I don't think it is simply that people know more. Enlightenment, for Kant, is not primarily a matter of knowing more. To put it in terms of virtues, which is a language Kant eschews here, enlightenment is about developing the temperament and character needed to judge claims fairly. It is by developing this temperament and character that intellectual freedom makes people ready for civil freedom.