Dye based ink pads are water based. They will run if they get wet and their colors aren't as vibrant as some other inks. However, they dry quickly and leave a very crisp image, good for detailed stamps. They are easy to clean, but some darker colors leave a stain. Stamp cleaning solution or baby wipes will get a stamp clean regardless of the colors that have been used.
Pigment based inks are also water based but, unlike dye inks, they contain little particles of color. They leave an impression that is more vibrant and more resistant to water (once dry) than dye based inks. They stay wetter longer so are suitable for embossing. They smear on glossy stock. A stamp inked with pigment ink can usually be cleaned with a wet paper towel but the darker colors may require the use of a stamp cleaning solution.
Embossing ink stays wet for very long time and is used only if you intend to emboss (using a heat gun) the image. It comes in a variety of colors and is available in a clear variety. Embossing ink is relatively sticky and should be removed with stamp cleaning solution or baby wipes. NON-oily