Confused about what Exactly an image feature is

Question

I read about image features on wikipedia and I am still confused about what exactly they are.
Term is explained in a manner such that I cant clear my confusion.

1. They represent a Class (edge is a feature and boundry is another)
2. They represent a instance of a Class(all the edges detected will be a feature)

Suppose I detect all the corners of an object and put them in an array say A.
Did I get only one feature or I got features=len(A).

Answer 1

Each feature is an individual "interesting" point or area in the image, with "interesting" depending on what algorithm is used to find features. In your example, you'd have A features, each of the corners being one.