What does it mean when a team has 'runners on the corners' in baseball lingo?

What does it mean when a team has 'runners on the corners' in baseball lingo?

Alan Jaeger (Pitching Coach / Founder) gives expert video advice on: What is a 'base runner' in baseball?; What do I do after I hit a fair ball?; After I hit a fair ball how should I judge how many bases I can take? and more...

In baseball lingo, when you say you have "runners on the corners", it simply means that there is a runner on first base and there's a runner on third base.