He is one of the founders of Y Combinator and the founder of Hacker News. pg was the moderator here for a long time.

For example: "Challenge HN: build pg-bot" https://news.ycombinator.com/item?id=2598026 (148 points | May 30, 2011 | 39 comments)

I never meet him, but apparently he repeat this kind of advice a lot, and someone of the first batches of YC made an image of a fake action figure of pg that repeats the advice when you press a button. I can't find the link :( .

Paul Graham, the cofounder of YC, whose website you are on.

> Am I supposed to know who PG is?

Yes, you are, if you're using the site he created (not to fault you for not knowing but often many HNers will reference Paul Graham by his initials so it's useful to know).

Paul Graham, the creator of this website.