Reflectors are among the simplest but most useful tools for portrait photography. They're also not too expensive, so it's one of the tools that beginner photographers are advised to get. These light modifiers come in different colors to suit different lighting needs or adapt to different kinds of light.
If you are shooting portraits, then you are probably doing at least a portion of your images indoors, especially during the winter months. You may be wondering how you can take advantage of available light indoors for portraits; maybe for stylistic reasons (you like the look of it better) or for other reasons (like not having to cart around a crap ton of lighting gear), whatever your reason is, it is totally possible to make the most out of available lighting for portraits indoors.