An internship is when you learn how to work in an office or company. A specific person gives you information about how to work in the office.
There will be times when you have to work on your own. If there is no one to guide you, then you will have to complete the work on your own.
In order to be successful at any job, you must have experience. You will not be hired if you lack experience because most companies don't hire people without it. If you want to get a job in a big company, then you should have work experience so that you can do the work well. This can be accomplished by doing an internship.
Regardless of the field of your interest, you get to learn a lot and gain a lot of experience by doing an internship.