A toner cartridge is a component used in laser printers and photocopiers to produce printed text and images. It contains a fine powder called toner, which is made from plastic particles, carbon, and coloring agents. When the printer receives a print command, the toner is transferred onto paper using heat and pressure, creating the final printed output. Toner cartridges come in various types, including standard, high-yield, and color cartridges. They are designed to be replaced when the toner runs out, and many printers have indicators to alert users when it's time for a replacement. Proper disposal and recycling of used cartridges are important for environmental sustainability.