The arts often have jargon languages of their own that newcomers can have a tough time cracking. Those working in the industry will often talk in ways that only other people in the same field know, this "special language" is quite extensive and can filter out into every area of craft. Here is a look at some of the more common digital photography lighting terms, concerning lighting through both artificial and natural means.
A spot light is a type of main light source that is incredibly focused and direct. This means that the light is going to be less diffused, more direct, and less sweeping over the entire subject. Te spot light can also be much more intense than more diffused forms of main lighting.
A bounce light is a light that is "bounced" from a reflective source onto the subject when considering lighting in photography. With a bounce light, the starting light source is not where the light on the subject is coming from directly, and the actual nature of the light is going to depend both on the starting light source and the source of the bounce surface. The bounce light is usually going to be much more diffused and even lacking in strong shadows, and is often used as a fill light.
The flood light is a reverse of many of the qualities of the spot light. Instead of being sharp, narrow, and focused, it is much broader and softer. The flood light is going to spread out over the subject and there are going to be less clean shadows. The flood light is also going to be good for lighting a larger area.
If a photographer is looking at their image and seeing that there are areas that are too bright, then they may say that those areas are "too hot." This does not mean an explicit heat in the image, but instead that some areas may be blown out in the final image or are just simply too bright for their specific purpose. This may end up being one of the most common digital photography lighting terms since it is said quite a bit while the image is being composed with light. You may also identify an area as being too hot when looking at or editing the photo later on.
Though this is not going to be exclusive to lighting in photography, if something is "soft" then it generally means that it is out of focus. This is going to be used in different digital photography lighting situations as the degree of lighting and position of lights is going to be directly correlated how you are focusing on an image.
Ambient light is photography lighting that is not inspired by you through unnatural means, which is to say that it is light in a given location before it is affected. Outdoor light is going to be ambient light, and unless you have complete control over a situation you are going to have some amount of ambient light in your shot. You can try to adjust the ambient light, eliminate it as best you can, or allow it to come in and be part of your image. Ambient light is not just a digital photography lighting term as it is something that is present often and discussed in a variety of disciplines.
Overexposure is, in essence, a more broad term for "too hot." This means that there is going to be too much light in an image for it to be properly exposed for the type of image that the photographer wants. This is going to be affected by things like shutter speed, the aperture, and the ISO setting and is important for lighting in photography.
Underexposure is the direct reverse of the overexposure in that it exists because of a general lack of light. If an image is constructed to have a certain amount of light, yet lacks that light then it is underexposed.
A backlight is a light that comes from behind the subject to illuminate their back, which is not primarily visible. Instead, the backlight is used to illuminate the edges of a person to cut them out from their background, allowing them to have a more full character. The backlight is usually positioned to one side and above the subject and pointed down at their back so that it will hit the back of their shoulders and head while still staying out of the photo frame. Read How to Use Backlighting to Enhance Your Photos to learn tips and tricks on this photography lighting technique.
The magic hour refers to a period of time during the day when the natural light coming from the sun is a certain way that is colorful and often appealing in a photo. This period tends to be dusk where the light is less than that of the day, but not yet absent into the beginning of the night. The magic hour can also refer to a period in the morning before the sun has arisen entirely.
The fill light tends to be a soft light that is going to "fill in" light on a subject where the dominant light key light does not. The key light is the strongest light, but much more specific and it is used to set the dominant perspective on the subject and define the main shadows. The fill light it to make sure that the rest of the object is lit, but does not reduce the shape of the image that was determined by the key light.
Ratio lighting is a term that simply refers to an uneven form of lighting on a subject to change the appearance to a specific decision about how the subject should look. What this means in a practical sense is that ratio lighting involves the negotiation between the fill light and key light so as to create a non-constant pattern of light on the subject.