Sleep apnea is a sleep disorder characterized by pauses in breathing or shallow breaths while sleeping. These pauses can last from a few seconds to minutes and can occur many times throughout the night. The three main types of sleep apnea are:

1. **Obstructive Sleep Apnea (OSA)**: This is the most common form, where the airway collapses or becomes blocked during sleep, leading to shallow breathing or pauses in breathing.

2. **Central Sleep Apnea (CSA)**: In this type, the brain fails to send signals to the muscles that control breathing, causing brief pauses in breathing.

3. **Complex Sleep Apnea Syndrome (or Treatment-Emergent Central Sleep Apnea)**: This is a combination of obstructive and central sleep apnea.

Common symptoms of sleep apnea include loud snoring, gasping for air during sleep, waking up with a dry mouth or sore throat, morning headaches, excessive daytime sleepiness, irritability, and difficulty concentrating.

Sleep apnea can have serious consequences if left untreated, such as an increased risk of high blood pressure, heart disease, stroke, diabetes, and other health problems. Treatment options vary depending on the type and severity of the condition and may include lifestyle changes (like weight loss or changing sleep position), CPAP (Continuous Positive Airway Pressure) therapy, oral appliances, or surgery in some cases.