What are the differences between glu, glew, glut, qt, sdl, openGL and webGL?

So I realize that there are various posts that cover pairs of these but I am having trouble understanding how they all fit together.

Explain what each of the following are used for and how they relate to each other:
glu
glew
glut
sdl
qt
openGL
webGL

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OpenGL

OpenGL (Open Graphics Library) is cross-platform API for rendering 2D and 3D graphics. The API mainly tries to focus on using the GPU to achieve hardware-accelerated rendering.

OpenGL-ES

OpenGL-ES (OpenGL for Embedded Systems) is a subset of OpenGL designed for use on embedded systems like smartphones, tablets, game consoles, etc.

WebGL

WebGL (Web Graphics Library) is a JavaScript API for rendering 2D and 3D graphics. WebGL also uses the GPU as much as it is possible through the browser.

WebGL is based on OpenGL-ES. Take in mind that they might have the same functions, though WebGL isn't OpenGL or OpenGL-ES. WebGL is only based on OpenGL-ES.

GLU

GLU (OpenGL Utility Library) is a graphics library for OpenGL, consisting of utility functions which can be used with OpenGL. The functions mainly focus on primitive rendering and mapping between screen- and world-coordinates, etc.

GLEW

GLEW (OpenGL Extension Wrangler Library) is a cross-platform library helps in querying and loading OpenGL Extensions.

GLUT

GLUT (OpenGL Utility Toolkit) is a library of utilities for OpenGL, which primarily focuses on window definition, window control and monitoring of keyboard and mouse input.

SDL

SDL (Simple DirectMedia Layer) is a cross-platform development library designed to provide low level access to audio, keyboard, mouse, joystick, and graphics hardware via OpenGL.

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SDL can also be used for other graphics API's such as DirectX, etc.

QT

QT is a cross-platform application development framework widely used for the development of GUI programs (in which case it is known as a widget toolkit), and also used for developing non-GUI programs such as console tools and servers.

Conclusion

• OpenGL is an API for rendering 2D and 3D graphics.
• OpenGL-ES is a subset of OpenGL targeting embedded systems.

• WebGL is a JavaScript API for rendering 2D and 3D graphics, based on OpenGL-ES.

• GLU is a utility library for OpenGL, which mainly contains mapping functions.

• GLEW is a utility library for OpenGL, which can handle loading of OpenGL Extensions.
• GLUT & SDL is a library for handling various things like window, keyboard and mouse control as well as listening.
• QT is a framework mainly for creating GUI.

Thereby GLU, GLEW, GLUT is simply utility libraries for OpenGL, which requires OpenGL, if not they aren't for much good.

SDL doesn't require OpenGL and isn't directly an OpenGL utility library mainly, but it can be used with OpenGL but also with other things as well.

[출처] https://stackoverflow.com/questions/19719055/what-are-the-differences-between-glu-glew-glut-qt-sdl-opengl-and-webgl