What is the Inner Core of the Earth?

About Earth’s Inner Core:

• It is the innermost part of Earth.
• It is located at the Earth's center, approximately 5,150 kilometers (3,219 miles) beneath the Earth's surface.
• It is a solid metallic ball primarily composed of iron and nickel.
• It makes up around 20 percent of the Earth’s mass.
• It has a radius of about 759 miles (1,221 kilometers).
• It is extremely hot,with temperatures ranging from 7200–9000℉ (4000–5000℃).
  • The primary contributors to the inner core's heat are the decay of radioactive elements such as uranium, thorium, and potassium in Earth's crust and mantle, residual heat from planetary formation, and heat emitted by the solidification of the outer core.
• It is under intense pressure of about 3.6 million atmospheres (atm), which keeps it solid despite high temperatures.
• It is surrounded by the outer core—a superhot layer of molten metals similar to those in the inner core—which is surrounded by a more solid sea of molten rock, known as the mantle, and the crust. 
• The boundary between the inner and outer cores is called the Lehman Seismic Discontinuity.
• The inner core generates its own magnetic field.
  • Despite its small volume (less than 1% of the Earth's volume), the Earth's inner core contains about 10% of the total magnetic field energy.
• It plays a crucial role in outer core liquid motions and the geodynamo, which generates the Earth's magnetic field.

It rotates in the same direction as the surface of the planet but a bit faster than the rest of the planet.

Q1: What is Mantle?

The mantle is the mostly solid bulk of Earth's interior. The mantle lies between Earth's dense, super-heated core and its thin outer layer, the crust. The mantle is about 2,900 kilometers (1,802 miles) thick, and makes up a whopping 84 percent of Earth’s total volume.The rocks that make up Earth’s mantle are mostly silicates—a wide variety of compounds that share a silicon and oxygen structure. The temperature of the mantle varies greatly, from 1000°C (1832°F) near its boundary with the crust, to 3700°C (6692°F) near its boundary with the core.

Source: Earth's core is now rotating in reverse direction, slowing down: What does it mean?