Wins71 - this is a huge subject and you will have to do some serious reading. In a nutshell, an option gives the holder the right, but not the obligation, to buy (call) or sell (put) the underlying asset at a fixed price (known as the strike price) on a set date in the future (expiry date).
I think the best place to start would be a good primer book. This one is as good as any, and better than most.
Options Plain and Simple by Lenny Jordan. Published Prentice Hall ISBN 0 27363878 5 at about £20.
The London International Financial Futures Exchange (LIFFE) site is a mine of information, and gives 15 minute delayed prices on all UK equity and index options for free - which is quite adequate for most purposes.
http://www.liffe-data.com/optionPrices.asp
Most option traders cut their teeth in the UK on the 76 (or so) optionable shares before moving onto the US, where there are over 2200 optionable shares! The equivalent to LIFFE is the Chicago Board Options Exchange (CBOE) which also gives 15 minute delayed prices. The main difference is the contract size (1000 shares in the UK, 100 shares in the US). Lots of useful
educational material here.
http://quote.cboe.com
and also :-
http://www.commodityworld.com/options_strategies.htm
http://www.numa.com/derivs/ref/os-guide/os-0a.htm
It is useful to have a good payoff diagram calculator. The one I use can be downloaded for free from :-
http://www.hoadley.net/options/LatestVersion.htm
You will need a reasonably up to date version of Excel to run it - I use Excel 2000. It does not run properly on pre-1997 versions.
There is an excellent series of online tutorials to use this calculator :-
http://www.hoadley.net/options/demos.asp
The basic position calculator is free, and although I say "basic", it is in fact incredibly sophisticated - esp for a freebie. I had a look at the additional programming you get for the princely sum of about £11, and it takes it on another quantum leap - probably more than most people will ever need, unless their style of trading is very frenetic.
It is absolutely essential to understand (and to be able to draw) payoff diagrams from first principles on a piece of paper rather than rely on the software. If the software shows that you have designed a strategy that looks too good to be true, then it probably is and you need to check the accuracy of your work!
You do not need to put up margin if you just want to buy an option. If you want to sell naked options then you need to put up margin, or cover the options with the underlying shares, as in a covered call trade.
Simply buying options is the toughest way to make money from options as you not only have to be right about the direction but also the time. A far better way is to both sell and buy options in various combinations (spreads, synthetics, strangles etc). Also remember that options are as much a play on volatility as they are on change in price of the underlying security (or index).
Now, go get yourself a good book and come back with more questions when you have mastered the basics! :cheesy: