Wraiths are the main air force of the Terrans. They can provide the best scouting out of the entire Terran army. Especially with cloaking, the wraith can act as an observer. The wraiths are very weak, so if you are detected you should run, and repair. However, they will slaughter anything as long as they are cloaked. Don't be afraid to send them out to watch over expansions, they'll be doing the same job as an overlord, yet you can always cloak and run away. Once you have 6-10 wraiths, you can deal some serious damage. Try to scan for weaknesses in someone's base. If they placed anti-air detectors at the edge, then take the risk and run through it, you will take heavy casualties, but if you survive with enough wraiths you can destroy his economy. Wraiths can have the same effect as lurkers and dark templars. If you choose to rush to wraiths, skipping any factory units, except maybe vultures, you can catch other players off guard. However you should build wraiths from multiple starports. Also you should build a few wraiths before attaching a control tower, probably construct the add-on on your second starport. This is only to get more energy by the time your wraiths obtain cloaking. Wraiths have a great air-air attack, so usr them to quickly kill specific units, since your opponent won't see them coming.