OpenCV is ubiquitous in some domains. It's like asking; "What's numpy?"

What's numpy?

Portmanteau of Numeric and Python. It's widely used Python library for matrix math and functions for operating on large arrays and matrices.

Gotta click to the about page.

> OpenCV (Open Source Computer Vision Library) is an open source computer vision and machine learning software library. OpenCV was built to provide a common infrastructure for computer vision applications and to accelerate the use of machine perception in the commercial products.

It sort of does in the first sentence "OpenCV (Open Source Computer Vision Library)", but they could really be a lot clearer about that. I really wouldn't give a crap about the license and implementation details until I had a fair idea of what the project could do for me.

Ever see a video of a computer tracking faces in a lobby or license plates on moving vehicles? That's what OpenCV is used for; making computers "see."

If for some reason you are unaware of the existence of OpenCV, just click "About" to get to a nice summary of what it's all about.