"Dave can get you $500 of your "future money" instantly."

That's called a loan. And, generally speaking, those sorts of loans have usurious interest rates. Let's go see what they are on the dave.com website. 

Well it doesn't tell us up front but every time they mention the $500 it has a superscript symbol (1) next to it. 

The ExtraCash™ account is a part of Dave’s pilot program and is open to new members only subject to availability. ExtraCash™ is a DDA account with overdraft utility that is subject to eligibility requirements. Taking an ExtraCash™ advance will make your account balance negative. Express delivery fees apply to instant transfers. See the Extra Cash Account Agreement for more details. 

A DDA account is basically a checking account. No advance notice is necessary to withdraw funds. 

They claim to have no overdraft fees and no minimum balance. Characteristics that bank accounts often have which restriction when and how you can use your money. 

It was founded by three guys who were fed up with banks, their terrible service and their high fees. 

I actually started this post being snarky about another dumb commercial I had seen too often while watching Paramount+ but it looks like Dave may actually be a good deal instead of a bank (which I actually hate, I have my money in a credit union nowadays).