Earth is the third planet from the Sun, the fifth largest and the densest major body in the solar system.

orbit: 149,600,000 km (1.00 AU) from Sun

diameter: 12,756.3 km

mass: 5.972e24 kg

Earth is the only planet can be studied without the aid of spacecraft, and of course is the most known one. The planet is divided into several layers which have distinct chemical and seismic properties (depths in km):

0-  40  Crust:

It varies considerably in thickness, being thinner under the oceans. That cape is where the humans live.

40- 2700 Mantle:

The massivest Earth's cape. Is sepparated in the "Upper mantle (40- 400), the "Transition Region" (400 - 650) and the "Lower mantle" (650-2700)

2700-2890  D'' layer:

The sepparation between the Mantle and the Core.

2890 - 6378 Core:

The inner cape. Is composed mostly of iron (or nickel/iron) and probably may be present some ligther elements. It temperature is extreme, around 7500 K (hotter than the surface of the Sun), and is divided in the "Outer core" (2890-5150) and the "Inner core" (5150-6378).

Taken as a whole, the Earth's chemical composition (by mass) is:  

34.6%  Iron

29.5%  Oxygen

15.2%  Silicon

12.7%  Magnesium

2.4%  Nickel

1.9%  Sulfur

0.05% Titanium

Most of the mass of the Earth is in the mantle, most of the rest in the core; the part we inhabit is a tiny fraction of the whole (values below x10^24 kilograms):

atmosphere: 0.0000051

oceans: 0.0014

crust: 0.026

mantle 4.043

outer core: 1.835

inner core: 0.09675

Unlike the other terrestrial planets, Earth's crust is divided into several separate solid plates which float around independently on top of the hot mantle below. There are (at present) eight major plates:

North American Plate: North America, western North Atlantic and Greenland

South American Plate: South America and western South Atlantic

Antarctic Plate: Antarctica and the "Southern Ocean"

Eurasian Plate: Eastern North Atlantic, Europe and Asia except for India

African Plate: Africa, eastern South Atlantic and western Indian Ocean

Indian-Australian Plate: India, Australia, New Zealand and most of Indian Ocean

Nazca Plate: Eastern Pacific Ocean adjacent to South America

Pacific Plate: Most of the Pacific Ocean (and the southern coast of California!)

The Earth is 4.5 to 4.6 billion years old, but the oldest known rocks are about 4 billion years old and rocks older than 3 billion years are rare. The oldest fossils of living organisms are less than 3.9 billion years old. There is no record of the critical period when life was first getting started.

71% of it surface is covered with water, so the Earth is the only planet on which water can exist in liquid form on the surface (though there may be liquid ethane or methane on Titan's surface and liquid water beneath the surface of Europa). Liquid water is, of course, essential for life as we know it.

The Earth's atmosphere is 77% nitrogen, 21% oxygen, with traces of argon, carbon dioxide and water. There was probably a very much larger amount of carbon dioxide in the Earth's atmosphere when the Earth was first formed, but it has since been almost all incorporated into carbonate rocks and to a lesser extent dissolved into the oceans and consumed by living plants. The presence of free oxygen is quite remarkable from a chemical point of view. Oxygen is a very reactive gas and under "normal" circumstances would quickly combine with other elements. The oxygen in Earth's atmosphere is produced and maintained by biological processes. Without life there would be no free oxygen.

The interaction of the Earth and the Moon slows the Earth's rotation by about 2 milliseconds per century. Current research indicates that about 900 million years ago there were 481 18-hour days in a year.

Earth's Satellite: Earth has only one natural satellite, the Moon. But thousands of small artificial satellites have also been placed in orbit around the Earth.

Asteroids 3753 Cruithne and 2002 AA29 have complicated orbital relationships with the Earth; they're not really moons, the term "companion" is being used. It is somewhat similar to the situation with Saturn's moons Janus and Epimetheus.
Lilith doesn't exist but it's an interesting story.

Moon:

Distance from Earth: 384.000Km

Radius: 1.738.000Km

Mass: 7.35e22Kg