Metamorphic rocks are named after the term metamorphism, which means 'to change'. These rocks are called so because they change from one form to another due to several external factors.
Parent rocks are the original rocks from which the metamorphic rocks are formed after undergoing changes.
Sandstone, limestone, and shale are all sedimentary rocks which change their form due to high heat, pressure, temperature, and chemical activity and form their respective metamorphic rocks.
Thus, sandstone, limestone, and shale are parent rocks and quartzite, marble and slate are the respective metamorphic rocks formed from them.
