If you are a student on financial aid, you may have severe consequences to dropping out. Your tuition has been paid, and depending on when you leave the program, you will be personally responsible for that amount. For example, if you left two-thirds of the way into the semester, this is considered past the point for the refunding of tuition. You will have to pay that money back to your lender. The university will not mark the amount cleared and you will not be able to get a transcript until you have made arrangements for the money owed.
If you received cash awards from loans, grants or scholarships to use for your living expenses while in college, you have disregarded your obligation and agreement for them. You will be unable to apply for or receive further grants until you clear this obligation by showing responsibility. Typically this means repayment arrangements and raising your GPA to standards set by your college that will meet eligibility requirements for applying for aid. The catch-22 that you will find yourself in is that your grades can potentially suffer when you drop out and you will find yourself below that standard.
All semesters have a drop period where students face no penalty for dropping classes. Check with your program, because this is usually within the first four weeks of the start of class. If you are dropping all of your classes, this is even more critical because you are leaving the university, and not just one or two classes. If you leave after the best drop period, you cannot withdraw with no penalty and you will be given failing grades for your classes. As previously noted, if your GPA is too low, you will not be allowed to apply for financial aid if you return.
If you decide that you would like to return to your university during another semester, you will need to reapply. Dropping out of all classes will drop you out of the university entirely, and you will be looked at as a new student, but one with a history. The tough part of this is you will be a student who potentially has a very low GPA if you left after the no-penalty drop period. In this case, if you are admitted, you will likely be on probation until you raise your GPA, and will be responsible for paying for your own tuition until you are off probation.