The tools typically work by scanning the PDF document for embedded image files and then extracting them to a separate file format, such as JPEG or PNG. Some tools may also allow you to specify the image resolution or quality, and to choose which pages of the PDF document to extract images from.
There are several standalone desktop applications and online services that offer PDF image extraction functionality. Some of these tools are free, while others require a subscription or a one-time purchase. It's important to choose a tool that is compatible with your operating system and meets your specific needs in terms of image quality, file format, and other features.