Screens have an actual grid of pixels. That’s really ideal when all the content on the screen is made of horizontal and vertical lines. What happens when a line is angled or curved? Those lines will look all jaggy as they’re depicted with those square pixels.
Enter anti-aliasing. This is the feature which adds grey pixels along those edges to make them appear smooth.
As screens gain increasingly high resolution, these pixels get smaller and smaller. That just means that these pixels are so small the eye cannot differentiate them with the device at a normal reading distance.
Why (when) Should I Care?
In your day-to-day life as a designer, you don’t need to worry about anti-aliasing too much. You don’t need to be concerned with it when creating vector graphics. Only low-resolution raster images are a concern—especially those with type in them.
In Photoshop, you can choose from various anti-aliasing settings while using the Type tool. Again, if you’re exporting as SVG, these are irrelevant. If you’re exporting for high-resolution displays, they’re irrelevant.
This is how Adobe describes the above settings.
- Applies no anti-aliasing
- Type appears at its sharpest
- Type appears somewhat sharp
- Type appears heavier
- Type appears smoother
This is the support page on Photoshop’s anti-aliasing settings, in case you’re interested.