Same-Day Funds
  
Even with electronic transfers and ATMs and all the other advances in communication and technology, sometimes, when you deposit your paycheck, you still have to wait a day or two to spend that money. You can get same-day delivery from Amazon in some places, but you have to wait on a check to clear. When that wait happens...those aren't same-day funds.
Same-day funds are, as you might guess, funds you can use that same day. Once you deposit them, you can transfer the money or take cash out of the bank immediately. There's no lag in the settlement of the checks.
Usually, this isn't the case. However, banks do have exceptions, i.e. times when they allow same-day funds. For instance, some banks allow same-day funds for paychecks from major payroll processing companies (although...most paychecks are processed via direct deposit, anyway). Meanwhile, banks also sometimes allow same-day funds for checks issued by that same bank; that is, by the same bank where you're depositing. Since they're only transferring funds from one of their accounts to another, they allow the same-day option. (It's all the same cash in the back; they just move it to a different pile. That's how banking works, right?)