The belts in tae kwon do mean the rank and experience you are at in you tae kwo do training.
The white belt symbolizes innocence. Its the start of your Taekwondo journey.
Your yellow belt represents the earth. It's like putting the soil in a pot for a plant to grow. In this case the soil is your basic taekwondo technique and the plant is your taekwondo.
Your green belt symbolizes the plant that is starting to grow. Your taekwondo techniques at this stage are starting to blossom.
Your taekwondo blue belt represents the sky. Your taekwondo plant is now growing tall towards the sky.
Red is for danger. Taekwondo red belts have lots of skill but may need to work on their self control.
And finally taekwondo black belt which represents maturity and rejection of darkness.