Here's a breakdown:

* Metamorphism: A process where existing rocks (igneous, sedimentary, or even other metamorphic rocks) are transformed by heat, pressure, and/or chemically active fluids.

* Metamorphic Grade: A measure of the intensity of these conditions.

* Low-grade Metamorphism: Rocks formed under relatively low temperatures and pressures. These rocks will exhibit minimal changes from their original form.

* High-grade Metamorphism: Rocks formed under high temperatures and pressures. These rocks will show significant changes in mineral composition, texture, and often have a more "banded" appearance.

Here's what you can learn from a rock's metamorphic grade:

* Depth of burial: Higher grades of metamorphism usually indicate greater burial depths.

* Proximity to a heat source: Intrusions of magma or tectonic activity can create high-grade metamorphic environments.

* Age of the rock: Metamorphic grade can be used to determine the relative age of rocks in a region.

* Mineral assemblage: Specific minerals are characteristic of particular metamorphic grades, which can help identify the conditions under which the rock formed.

Examples of metamorphic grade:

* Low-grade: Slate, Phyllite

* Intermediate-grade: Schist

* High-grade: Gneiss

By studying the metamorphic grade of a rock, geologists can learn a lot about the geological history of the area where the rock was formed.