hiragana katakana difference?

What's the difference between those two alphabets? Why is it that there are two alphabets and not just one big alphabet? I searched for more answers on here but couldn't find anyone who had asked it already. Thanks in advance.

This isn't the only place for information on the internet! Have a look at this page http://en.wikipedia.org/wiki/Hiragana and then click on the katakana link, or try a Google search yourself if your questions are still unanswered.

how do you tell the difference? how do you know when to use katakana, is it just for foreign words? what if you're not sure if a word is foreign?

Hiragana and Katakan LOOK very different from one another so there is no mistaking which is which, even when you are just starting to learn them. When to use Katakana is something that you will learn as you learn it. There are no definitive precise rules. Your question is like asking "how do you know that a word is masculine or feminine in French?" there are no rules and you cannot tell just by looking at a word. You learn the right gender by using a word again and again. Some French people never get it right. but most children or foreign adult students learn it by speaking the language daily for about 4-5 years. .

Basically you learn these things through an in depth study of the language. It's not something that can be explained in a few sentences on an internet forum. If you see a word like バナナ (ba-na-na) written in katakana it is usually fairly obvious that it means banana and isn't a native Japanese word. In other cases it isn't so obvious.

okay. thanks to both of you for explaining as much as you could. im practicing everyday. thanks again.