The following explanations and definitions are taken directly from the Scottrade web site.

Stop Orders: Stop orders are an order to buy or sell a security when its price surpasses a particular point, limiting the investor's loss or locking in his or her profit. Once the market price surpasses the predefined entry/exit point, the stop order becomes a market order, and is then handled as defined under the definition of a market order.

This type of order is also referred to as a "stop-loss order". These types of orders also may NOT be placed with AON (all or none), but CAN be placed as GTC (good until cancelled) or GTD (good til date).

Stops are not a definite guarantee of getting the desired entry/exit points. For instance, if a stock gaps down then the trader's stop order will be triggered (or filled) at a price significantly lower than expected.

• Buy Stop Orders - The stop price is set above the current ASK price
• Sell Stop Orders - The stop price is set below the current BID price
• Depending on market conditions, once the order is triggered, there is no guarantee of the execution price and the price received may be several points away from the stop price.

Stop Limit Orders: This is a type of order that combines the features of stop order with those of a limit order. A stop-limit order will be executed at a specified price (or better) after a given stop price has been reached. Once the stop price is reached by the market, the stop-limit order becomes a limit order to buy (or sell) at the limit price or better. This order is then handled as defined by a limit order.
The primary purpose of a stop-limit order is to give the trader more control over where the order should be filled. The downside, as with all limit orders, is that the trade will not be executed if the stock does not reach the limit price.  These types of orders also may be placed with special instructions, like GTC (good until cancelled) and GTD (good til date).

Stop limit orders are used by some investors to buy a stock when it reaches a certain price, allowing the investor to buy when the stock has upward momentum behind it.

Buy Stop Limit Orders must be placed at least 10 cents above the current ASK.

Sell Stop Limit Orders must be placed at least 10 cents below the current BID.

Trailing Stop Order: This is a complex stop order in which the stop price is set at a fixed percentage or dollar amount above or below the market price. If the market price rises, the stop price rises proportionately, but if the stock price falls, the stop loss price doesn’t change. A Trailing Stop is a Stop Order that is set at an amount below (for a long position) and above (for a short position) the market price. The amount is automatically adjusted as the price of the security fluctuates.
The Trailing Stop order is designed to let the price of a stock go up indefinitely (in the case of a long position) and close the position when the price falls a set amount, potentially protecting the client from losing profits.  Trailing Stops can be entered as a sell to protect the downside of a long position, or as a buy to protect a short position. 
General Requirements:

• Only on Equities trading over $1.00 per share – NO Penny Stocks or Pink Sheets
• Only for the Regular Trading Session, does not cover the Extended Hours
• Orders will be adjusted for cash dividends
• You may place GTC (good until cancelled) instructions

Trailing Stop Amount Requirements:
Points – The dollar spread between the current market price and the order trigger price, which is entered in the “trailing stop amount field”

• 1 point = $1.00
• Points entered may be in one-cent increments
• The minimum point spread that can be set is .01; meaning 1 cent
• The maximum point spread allowed  is an amount equal to the stock’s price

Percent – The percent spread between the current market price and the order trigger price, which is entered in the “trailing stop amount field”

• Percent amounts may be entered in 1% increments
• The minimum percent spread that can be set is 1%
• The maximum percent spread that can be set is 99%

Note: Do not translate and enter the percent in decimal format. Enter 1 for 1%; do not enter .01 for 1% 

A word of caution: A considerable number of brokers calculate trailing stops on the last close and do not adjust throughout the trading session. Consider a stock that runs up from $20.00 to $28.00 during a single session and then retreats back and closes at $21.00, you will not be stopped out with a 5% trailing stop calculated on this basis, because price is still above yesterday's high, even though it has fallen 25% intra-day. Check with your broker about how  trailing stops are calculated.