I was told this was "Like In-N-Out, but different", and that's true, of course. I guess it's as good a description as any to get you started.
There are 2 standard sizes of burgers, the "small" is fine, as it's a single patty (the normal is 2 patties). These are way bigger than In-N-Out, if that's what you're comparing to. Bacon and/or cheese cost extra.
Fries are also much bigger and, I think, better than In-N-Out. Plus, you get a TON of them. Order 1 small fries for 2 people and you'll be fine. Try the Cajun flavor, they're not bad.
You can top your burger with any of 15 or so toppings including the standards like tomato, etc. but also some good ones like Green Peppers, grilled onions, and jalapenos. No charge.
If you're dining in, get a soda, just to try out the pretty awesome computerized soda fountain machine. They advertise "Want Orange-Coke with Peach flavor? You can have it." and you really can.
One more comparison with In-N-Out... 5 Guys is a bit more expensive. A small burger + fries + drink will get you for almost $10. It'll be more food than the $5 double-meat combo at In-N-Out by a bit, but not double.
Bring down the price to $8 for the meal, and I'd throw the 5th star up there. Maybe 2 meals for $16 (saving one fry order) would do it.