Different people have many different ideas about what constitutes a public hearing, so keep that in mind whenever you're talking about these things with other people. For the purposes of this section, we're going to define public hearings in two ways:
A public hearing may be a formal meeting for receiving testimony from the public at large on a local issue, or proposed government action. Testimony from both sides of an issue is usually recorded for public record, and a report summarizing the key points is generated. All levels of government hold public hearings - from city on up to the national level. Sometimes, formal public hearings are mandated by law (on the environmental impact of a proposed highway project, for example). In other cases, government officials use them to gather information that will help them in making decisions or drafting legislation.
A public hearing may be less formal - it may or may not be sponsored by a government body - and it doesn't require that both sides of an issue get time to speak. You may choose simply to have a panel of people discussing an issue, with or without a question-and-answer period.
Public hearings are sometimes also called accountability sessions or study sessions. In official, formal hearings, laws may require high standards of fairness and the whole thing may feel more like a courtroom.