What does this mean...?

[j_miguel_y]

I always wondered what the purpose and use for adding a question mark after a certain URL.

For example: www.yahoo.com/login?.rand=86g3bdk9a0pdc

What is the question mark for, and the rand = for?

What is this term called, and why is advanatgeous?

Thank You

[LordShryku]

It's called GET. It's a way of passing information to other pages.