Sensitive describes something or someone who reacts quickly and strongly. It's often something to protect — like baby skin, government documents, or a fragile ecosystem.
Anything sensitive should be treated with special care. It can mean "raw or hurting" when talking about a part of the body. After people visit the dentist, their gums are often sensitive because of the way that big angry lady cleaned their teeth. Sensitive people get their feelings hurt easily. Sensitive documents have big secrets that shouldn't get out. A sensitive tape recorder catches all the little background sounds. Now you should have a sense of the word sensitive.