Employment is work performed in exchange for compensation. Compensation can include money, room and board, or other benefits. Volunteer work is unpaid. You are eligible to volunteer for non-profit charitable organizations. But you still need to check with IPS before you do.
Before accepting any kind of paid or volunteer position, contact International Programs and Services to be sure it is allowed.
Post Graduation Employment
Remember that IPS does not provide any advice regarding H1B. You must consult with your company's HR department or lawyer and/or an immigration attorney.
If you are transitioning from OPT to H1B, please visit the 12-Month OPT or 24-Month OPT page (as applicable) and scroll down to the section that says "Transitioning from F1 to OPT". Make sure to fill out the H1B Approval Notice form before your H1B begins.