Trill is a way of playing or singing music that sounds like a little shake in the notes. Imagine you have a toy car and you shake it really fast, up and down, and it makes a buzzing sound. That's what a trill sounds like in music.
When musicians or singers want to add extra emotion or expression to a note, they might use a trill. It's like a special effect or decoration on the note.
To do a trill on an instrument like a flute or a violin, you play the note quickly back and forth between the main note and a higher or lower note nearby. It's like wiggling your finger on a string or moving your lips on a flute. This makes the note sound shaky and buzzing.
For singers, a trill is when you quickly alternate between two notes that are very close together, like "la-la-la" but really fast. It adds a little bit of fancy flair to the singing.
So, trill is just a fancy musical decoration that makes the notes sound extra cool and emotional.