A sketchpad is a book with many pieces of paper where you can draw pictures.
Sketchpads are usually used by artists or people who like to draw.
Examples:
She draws a picture in her sketchpad.
I have a new sketchpad with lots of blank pages.
He carries his sketchpad everywhere he goes.
The sketchpad is full of colorful drawings.
I have a sketchpad for drawing animals.
The sketchpad is where I keep all my drawings.