If you have a front load washer, it comes equipped with a pretty extensive door gasket. This plastic piece functions as a seal to keep water from leaking out. However, the way it is designed means that it features a hollow area in the center where wash water can end up. Because this wash water needs to be removed, the seal also has a door drain in it. These drains are often very small, sometimes they are no bigger than a small hole or series of holes. While that helps keep them out of the way, they are prone to get clogged with lint and pet hair which leads to the need for this particular washer repair.
In many cases, you can pull obstructions out of these drain holes to unclog them. However, if you notice a lot of standing water in the gasket after a load, you need to take action in order to prevent mold and bacteria from growing wild in there.
Luckily, cleaning the gasket drain is actually pretty easy once you know how to take the gasket off. The most difficult part is to remove the clamp on the front of the gasket. They make special pliers that make this easier, but without them, it is a challenge to pinch together the clamp so you can take it off. Once done, though, the gasket peels right up. You will then find a drain hose behind the drain area. This should have hose clamps you can remove so you can disconnect it and clean the hose.
Aside from getting the gasket clamp off, the second most difficult thing is making sure everything goes back on tightly. If your gasket is very dirty, you may want to just consider replacing it as most of that repair is already done to clean the drain hose.