Heartburn is a form of indigestion felt as a burning sensation in the chest when stomach acid comes back up into the esophagus. Some people take an antacid to relieve heartburn. Which best describes the antacid's effect?

The antacid is basic so it neutralizes acidity or lowers it. Then if it goes into the esophagus, it's not as strong and it doesn't hurt, and it also calms your stomach because the acidity in your stomach is also lower. Antacids are therefore taken by many people, especially as they grow older and things like heartburn become more common.