A practicum student is a student doing an internship. Internships are always a great way to get hands-on experience in your field and match your theoretical knowledge with practical know-how.
There are internships available for most areas of education. Some of them are paid, some of them are a part of your curriculum, earning you valuable credits. Whatever the case, internships also provide an excellent opportunity to make professional connections, get some recommendations, or sometimes even get hired.
Your duties widely vary, depending on your field of study, but you are never left alone with situations you are unable to handle. You generally shadow or observe a professional or field instructor to make sure you are eased into your responsibilities gradually.