Hi Juliana, Under is used when something is directly under another item. For example, the cat is under the bed. Underneath is often used to say that something is covered by another thing. For example, our cat is underneath the pile of clothes. Beneath has a similar meanings as under or underneath, but it's a formal, literary word and there can be an element of something "hidden" when we use the word beneath. For example, we often wonder what lies beneath. We don't use this word much in speaking but it is used in film and literature.