What causes maturity risk? In other words, why do long-term bonds respond differently to interest rate changes

Question:

What causes risk? In other words, why do long-term bonds respond differently to interest rate changes than short-term bonds?

Maturity
Maturity is the date on which the life of a transaction or financial instrument ends, after which it must either be renewed, or it will cease to exist. The term is commonly used for deposits, foreign exchange spot, and forward transactions, interest...