Question

what are silent letters

Answer 1

silent letters are letters in a words that are written but not pronounced while speaking that word

Answer 2

The letters which are not to be pronounce with a word although that letters are used in a word.
Examples:
Car : here we cant pronounce the letter 'r' so it is the silent letter
Chalk: here we cant pronounce the letter 'l'. so it is the silent letter in this word