It's pretty simple actually. You get to set all the terms and duration before it's live to the public.
The fees vary depending upon the starting bid price, the final sale price, and any extras you added to the listing (such as bold lettering, themes, reserve prices, etc.). The total amount of initial fees are disclosed before you start the listing, although the final-value fee obviously won't be determined until it ends.
If you set a reserve price and it is not met, then the listing will end with no winners and no obligation to sell it. eBay does offer an option to sell it to the highest bidder afterwards should you choose to do so, otherwise you can either relist the item at a lower reserve or just not sell it at all.
There's something you should be aware of when it comes to selling on eBay...
The seller has very little recourse when it comes to disputes. eBay has tipped the odds in buyers' favors most of the time, so be prepared to cover all aspects of your listing.
eBay will not allow the seller to post negative feedback about the buyer. Only the buyer can post negative feedback. Don't ask me why, it's something they did not too long ago and it's the sole reason I refuse to sell anything there now.
Make sure you take thorough pictures of your item, including showing that you boxed it and labeled it properly. ALWAYS purchase insurance and delivery confirmation, even if the buyer refuses to pony up for it. Without insurance or delivery confirmation, the buyer can simply report that he never got it and he will receive both your item and a complete refund from eBay, with the funds being withdrawn from your bank account.
Although this is purely up to you, I suggest accepting payments only through PayPal, force the buyer to submit payment through PayPal immediately before the auction closes (there's an option for that during the listing process) and mention in the item description that you will only accept payments from Confirmed Addresses. Confirmed addresses are those that have been verified through the buyer's credit card or through other official means. This will help in avoiding some stolen credit cards being used to win your item. Accepting only PayPal gives you an extra layer of protection as well.
Just a few tips there. I have more if you have other questions.