What do interlace and non-interlace signals mean?

To understand this concept you have to understand the different types of tv. First you have CRT (cathode ray tube) This type of tv is usually interlaced and is the style that most people have. It has been around since the beginning of TV. The next style is the LCD/Projection/Plasma. These TVs are all progressive or non-interlaced. Cathode Ray Tubes display a picture by shooting a cathode ray at electrons giving you a picture. The cathode ray scan down the screen in lines. If it scans interlaced it will scan lines 1,3,5,7 etc. and then it will go back and scan lines 2,4,6,8 etc. Because of our mental ability to "fill in the gaps" we percieve it as an uninterupted picture. Non-interlace pictures scan all lines from top to bottom. Progressive scan gives you a higher quality image but it is harder to maintain brightness a constant picture because it takes longer to get through all of the lines than just half of them. This scanning rate is also called the refresh rate. Plasma screens and LCD essentially refresh all of their pixels at the same time so they are neither progressive nor interlaced.