Serif fonts have small lines at the edges of letters and symbols that make them easier to read in printed works, while sans serif fonts do not have these small lines and are better suited for digital screens like the web. Specifically, serif fonts aid readability in print but can be harder to read on screens, while sans serif fonts are clearer on the web but less suitable for print. Serif fonts should be used for body texts and printing, and sans serif is preferable for children learning and digital displays.