What is a ratio?

This unit in math I've been learning about ratios and the word has been thrown around a lot, but I still don't understand what a ratio is.

A ratio is a numerical comparison between 2 similar objects, persons, figures, or ideas. For example if I have 5 cards and you have 10, I can say that you have twice as many cards as I do. Or take my 5 cards and multiply by 2 to get your 10. Another way I can say it is that the ratio between your cards to my cards is 2 to 1 or 2:1 (both mean the same thing). Let's say now I have x cards, but knowing that I have a 2:1 ratio from your cards to mine, I can say that you have 2x cards. There is alot more I can say, but this should get you started. Feel free to ask any following questions.