Student IDs almost always have a few things in common. Each ID usually has the student's first and last name as well as a middle initial. IDs also sometimes include the student's birthdate, a headshot of the student and a student ID number (a number assigned to each new student that is different from a social security number).
Student ID cards are sometimes used by professors and teaching assistants as a means of checking the identity of students prior to distributing exams and finals. This is especially common in large lecture-style classes and intro courses in the sciences that serve as prerequisites for upper-level courses. By checking student IDs prior to distributing tests, one can ensure that the student enrolled in the class is the student showing up to take the test.
Many college and universities allow students or parents to "load" the student ID with money during the semester, making it somewhat like a credit card in that a student could potentially buy books with a swipe of their student ID. The cards are also often used in college dining facilities. With a single swipe, the cost of the meal can be deducted from the remaining balance on the ID card. Students can usually put as much money on their ID cards as they want. Many colleges and universities have an office in either the student center or student union that deals with matters pertaining to student IDs where students can deposit more money onto their card.
It's increasingly the case that businesses are beginning to offer student discounts to local college students. Some college towns even allow students to pay for goods and services with their student IDs. In order to get the discount, students must present the ID card at the time of purchase. Examples of businesses which sometimes offer student ID discounts include local restaurants, spas, gyms, computer repair shops and tanning salons.
Colleges and universities recognize that accidents happen and sometimes student IDs can get lost or stolen. Replacement IDs can sometimes be made for free, but more often than not, most colleges will charge the student a small fee for a replacement card.