I hear a lot about people self-quarantining. what does that mean? are they with their families? do they have contact with people bringing them meals or food? what about the mail?

Quarantine/isolation: Self-quarantining "separates and restricts the movement of people who were exposed to a contagious disease to see if they become sick" per the HHS. These people are often with their families, receive mail & may or may not have contact with others. Per HHS- "Isolation separates sick people with a contagious disease from people who are not sick."