The Marianas Trench is the deepest part of the Earth’s oceans, and the deepest point on Earth: 36,400 ft (11,033 m) deep.
It is located in the Pacific Ocean, about 200 miles (320 kilometers) south-west of Guam, which is part of the Mariana Islands.
The trench is about 1,580 miles (2,550 kilometers) long and has an average width of 43 miles (69 kilometers).
It was created by ocean-to-ocean subduction, a phenomena in which a plate topped by oceanic crust (in this case the Pacific plate) is subducted beneath (moves under) another plate topped by oceanic crust (the Mariana plate).
The Marianas Trench was first sounded during the Challenger expedition (1872-1876), which recorded a depth of 27,000 ft (8,184 m).
In order to better illustrate the actual depth of the Marianas Trench, consider the following: if Mount Everest, which is the highest point on Earth at 29,200 ft (8,848 m), were set in the Marianas Trench, there would still be 7,200 ft (2,183 m) of water left above it.