Giving someone a facial is when someone ejaculates onto the face of their partner. They are referred to as facial cum shots and are very popular in porn, making them a great finish if your partner is giving you the porn star experience (PSE).
As a facial requires one to cum, it is often the final act of sex, and so you will be positioned in a way that the semen will land on your partner's face, perhaps even after a blowjob (covered or uncovered) or hand job. For many it is a case of their partner kneeling before them on the floor, while they stand in front of them. This makes it easier to direct exactly where your cum will go.
The idea of giving your partner a facial is a turn-on because it is taboo. Some may see the act as degrading for the receiver, but many feel that this makes them the ultimate porn star, as they are able to do what porn stars do. Some feel it is a way of showing their appreciation, not only for the person but also their skills. It can be a huge turn on to do something taboo, hence why it is becoming more and more popular.
The most important thing to remember is to discuss the idea with your partner. If they are open to it, check with them later that this is still okay. There is nothing more shocking then a surprise facial cum shot, so give them some warning. It will give them time to close their eyes and prevent your spunk getting in them (which can sting and lead to infection), so let them know. Perhaps even suggest they wear some sexy secretary glasses to finish off the look. When you are getting close, let them know so that you can get yourselves into the optimal position. It will be an image you won't forget any time soon!