The edge of something is where a flat surface ends. It usually forms a 90-degree angle going down, but not always. Take a look at this picture:
This girl is resting her arms on the edge of the table.
The word "edge" is often used as a noun:
The little boy fell off the edge of his bed.
Our cat likes to sit on the edge of the table.
A razor has a very sharp edge.
The edge of a knife is also sharp.
A long time ago, people used to think that the world was flat and if they went too far, they would fall off the edge.
The train depot is located on the edge of town. ("The edge of town" is the near the border or the city limits.)
Powerful telescopes allow astronomers to see what the edge of the universe looks like.
Alice has an edge over the other applicants for the position because she speaks three languages fluently. (To "have an edge" is to have an advantage over others.)
Nate likes to live life on the edge. (To live on the edge is to do things that are dangerous, new, experimental, or challenging.)
You can also use "edge" as a verb in some idioms:
Bill edged out the competition and won first prize. (edge out = win; beat slightly)
We’re all on the edge of our seats awaiting the news. (on the edge of one’s seat = to anxiously wait for the outcome of something)
The company is edging forward with its plans to build a new headquarters. (edge forward = move forward, go forward, move ahead but slowly.)
