For anyone needing an explanation: most of the time, when you look for a font to use or download, you probably would like to see what every single letter in the English alphabet looks like with that font. However, just having 'abcdefghi....' is not a very good representation of how the font would look like in practice. So, people have come up with something called pangrams - a sentence that uses every letter of the alphabet at least once - which achieves both of those purposes. The most famous pangram is probably 'The quick brown fox jumps over the lazy dog', which is what the author of this quote is referring to, but there are a lot of other ones as well! Do you think you can come up with a sentence that uses every letter?