A surgical drain is meant to keep fluid or infectious material from building up at or near the site of a surgical procedure. It does exactly what it sounds like it does: drains blood and fluids away and out of the body, just like a plumbing drain.
There are many types of surgical drains, ranging from chest tubes that keep fluid from accumulating around the heart after open-heart surgery to small, bulb-type drains that apply gentle suction. The bulb can be secured near the bandage or attached to your clothes with a safety pin.
The type of drain you will get depends on the type of surgery you will have, what part of your body the surgery will be performed on, and the personal preference of your surgeon. You may have one drain or several, depending on the nature of the problem.
The large drains are not painful to have in place. But they can cause discomfort, depending on how big they are and where they are placed. Typically, the discomfort is mild. But it's fair to say that the larger the drain, the greater the likelihood that it will cause some pain.
For example, after heart bypass surgery, many people report that chest tubes were more uncomfortable than chest incision.
If you are sent home with a drain, be sure to protect it, making sure it doesn't dangle freely or in such a way that it could be accidentally dislodged. Some drains come loose when too much weight is placed on them.