Draw five horizontal lines equally spaced. You have a stave.
Draw ellipses over the lines and in the spaces. The higher the ellipse the higher the pitch. Music rises and falls on the page as it does in your ear.
Which instrument would you choose to play these notes? High pitched instruments and voices use treble clef. Low pitched instruments and voices use bass clef.
The clef is an ornamental symbol drawn far left of the stave.
You may meet many clefs in your travels. Let us introduce two more.
When you write for viola and alto voices you use alto clef. In classical music the alto clef is also used by trombone.
When you write for tenor voices you use tenor clef. Cello, bassoon and trombone use tenor clef occasionally.
Have a listen to the range of notes in each clef. Press the MIDI button.