What is the shallow, gently sloping area of the ocean floor that extends outward from the shoreline?
The continental emerged lands are surrounded by what is called "continental shelf" which is a relatively gently sloping (0.5 degree) surface of the seafloor.
The depth of the shelf is usually within 150 meters and during the ice age (with the ocean level lowered due to the sequestration of water within the ice shield) most of the shelf was emerged allowing migration between areas that instead now are separated by the sea. As example some coastal islands and mainland were connected.
The shelf is covered by sediments which were put in place during the ice age; other sediments are currently deposited by rivers from the emerged land.
The shelf ends at about 140 m of depth with an increase of the slope (up to 10 degree) that is called "shelf break" leading to what is called "continental slope". This area is often cut by deep canyons originated by undersea landslides.
Below the continental slope, there is the continental rise and, finally, the abyssal plan.
The continental shelf has economic importance for the fishery industry and for offshore hydrocarbons (oil and methane) production (as example the North Sea and Adriatic Sea).