A short list of words related to pygame, with brief definitions, arranged alphabetically.

Blit
to copy a large section of image data from one surface to another. This is how you draw a sprite on the screen. A blit can do some blending, which means not just overwriting the old image data, but changing it instead. This can be used to implement semi-transparent objects.
Dirty Rects
A rectangle area of what has changed on the screen. Called dirty rects because the rectangle has been dirtied - modified. Useful for speeding up screen redraws, because if only part of the screen has changed, then you only need to update part of the screen.
Screen
what the user sees.
Sprite
a visual object, capable of moving around the screen and being animated. Pygame provides a simple sprite class and several Group classes to organize sprites.
Surface
an object that represents graphical information. Loaded image data (.png, .jpg, .bmp) is stored in, and Surfaces can be written out to image files. In Pygame, the screen is a surface too.