In your own language you know many words that sound the same but do not mean the same. They are homophones (= "same sound"). In English, too, there are many homophones, and it's important to try to learn and understand them. We use homophones all the time, even in everyday speech. They are also a common source of humour in jokes, and frequently occur in riddles.
These pages explain homophones and give examples with audio, and also list many homophones by level and by type.