In terms of debt and equity, what are the differencess between stocks and bonds?

Which security is least reisky for the company? Why?

I could use an answer tonight if at all possible.

A share of stock is ownership in a company... you have claim to all
assets of the firm after every non-owner's claim has been satisfied.
This is sometimes referred to as a residual claim (because you claim
whatever's left after everyone else). Because of this structure, your
stock has theoretically unlimited upside value. Also, stock is
ownership, thus you get to exercise ownership control by voting.

A bond is like any other debt... it's a fixed contract. The company is
obligated to pay you interest and return the principal. Once they've
done that, your relationship to the company is terminated. So there's
no upside potential to owning debt. On the other hand, your debt is
theoretically secured by the company's assets, so its less risky than
stock.

Thank you this is very helpful. I am confused at how I pay for
comments verses answers. I think I should pay for this...to me it is
an answer. Please advise..

Financeeco's comment is informative, but does not answer your last question.

"Which security is least reisky for the company? Why?"

When a company takes out bonds, that is debt they owe.  Even if the
company doesn't do as well as they hoped, they still owe that money
back.  This debt might be a contributing factor in them going bankrupt
or having to sell off assets.
However stocks are not debt.  Stocks gain or lose value along with the
company.  So when the company does good, the stock value goes up.  If
the company does really poorly then the stock value goes down. 
Therefore there is no risk to the company with stocks.  Stocks will
never (not that I know of anyways) bankrupt a company.

And for your comment, there is no way for you to pay for comments. 
Financeeco and myself are not google researchers and so there is no
way for us to "answer" the question.  We can simply provide comments
to try to help out.

If you're happy with the info you have then you can close the question
so that you don't ever have to pay for it (asside from the $.50
posting fee), or you can leave it open and potentially a google
researcher will give you a much better written and better referrenced
answer that will be more worthy of the $5 :)