There are three common screen sizes in the notebook industry: 13 inches (33 centimeters), 15 inches (38 centimeters) and 17 inches (43 centimeters). The smallest in this group of laptops obviously prioritize portability, and often forgo DVD drives to make their bodies thinner and lighter. The mid-size category has a bit more range: Some heavier systems operate as desktop replacements, while others are light enough to still be easily portable while offering large screens. The largest category of laptops are, well, pretty huge. They always offer high resolution displays and powerful hardware, but can easily weigh up to 10 pounds (4.5 kilograms).
Generally, 15-inch (38-centimeter) and especially 17-inch (43-centimeter) laptops are large enough to be decent TV/computer monitor substitutes for watching video, especially on the go. Smaller notebooks, measuring 11 to 14 inches (27.9 to 35.6 centimeters) may be a bit small for watching movies, depending on your personal taste. More importantly, their displays are often lower resolution. The resolution is the total number of pixels contained in the display -- more pixels allow for more content to be displayed on screen at once.
Resolutions typically range from 1366 by 768 -- just a bit larger than 720p -- to 1920 by 1080, aka 1080p. Laptop makers will often use lower resolution displays to cut costs. On the next page, we'll get into the processor and graphics card, two other critical components. But if you're comparing two computers, go for the higher resolution screen when possible, or choose an HD upgrade option if it's available.