Graphics

Text Mode
Text mode is fast technology. The screen has 25 lines, 80 columns -- 2 bytes per character, one for ASCII code and one for the character attribute. It can have no more than 4000 bytes. In video memory it has the ASCII value and it looks in ROM of the video CPU to look at the way the letter looks. Then, it puts it on the screen. This takes little processing, but some features cannot be used.
Graphics Mode
Graphics mode uses images and pictures, not only text.
Pixel
A picture element or dot on the screen
Resolution
Measures the number of dots across and down the screen. A typical VGA screen is 640x480.