RGB stands for Red, Green, Blue — the 3 primary colors of light. Every pixel on a computer monitor, phone screen, or TV combines these 3 channels at varying intensities (0-255 each) to produce up to 16,777,216 visible colors. At R:0 G:0 B:0, all channels are off and the pixel is black. At R:255 G:255 B:255, all channels are at full power and the pixel is white.
RGB is an additive color model: mixing red and green light produces yellow, mixing all three at full intensity produces white. This is the opposite of print, where mixing inks subtracts light and produces darker colors. That fundamental difference is why screen colors never perfectly match printed output.
Designers work in RGB when building websites, apps, and digital graphics. But the moment those designs move to print — business cards, posters, packaging — the colors need translation into a physical ink system like the Pantone Matching System (PMS). That is where RGB to Pantone conversion becomes a required step.