RGB and CMYK are different colour systems, and choosing the wrong one can affect how your design looks.
RGB and CMYK are not interchangeable terms. They are colour modes built for different environments.
RGB is used for screens
CMYK is used for print
That difference matters because colours can appear differently depending on where they are being displayed or produced.
RGB stands for Red, Green, and Blue. It is the colour system used for digital displays such as:
websites
social media
screens
presentations
digital graphics
RGB usually appears brighter and more vibrant on screen.
CMYK stands for Cyan, Magenta, Yellow, and Key (Black). It is used in physical print processes.
This is the colour mode generally used for:
flyers
business cards
posters
brochures
packaging
printed signage
A bright colour seen in RGB may not print exactly the same in CMYK. That is normal.
Print has different physical limitations, so certain colours may shift slightly when moved from screen to print production.
RGB is for screens. CMYK is for print. Mixing them carelessly is one of the easiest ways to end up with colour surprises you did not ask for.