From SC2Pod
The Warp Gate is an upgraded version of the Gateway that, in short, allows players to quickly bring in new units anywhere that there is pylon power owned by the player (i.e. it can not be used where there is only ally or enemy power). If the pylon power is lost while units are being warped in, the units are canceled and the resources they cost are refunded.src
Dustin Browder does a good job explaining it in detail:
Cavez wrote: (source)
- You build Gateways.
- You purchase the Warp-In upgrade on the Cybernetics Core.
- You select your Gateways and transform them into Warpgates. This is extremely fast.
- You may select your Warpgates and transform them back into Gateways (also fast) any time you want. You would mostly do this if you wanted to reduce your Macro and rely on queues. Skilled players never go back to Gateways once they have Warpgates.
Now that you have Warp Gates:
- Select a Warpgate.
- Select a unit to build.
- Target anywhere within a power radius.
- Unit begins to warp-in where you selected.
- Warp-In is very fast.
- Unit is vulnerable during the warp-in process and can be killed before the warp-in is complete.
- Warpgate must now "cooldown" with a time equal to the build time of the unit created before it can warp-in again.
That's how it works right now. In games it is extremely effective with Immortals and Dark Templars though I have seen it used with everything at one time or another..
Combined with the MBS mechanic introduced to SC2 the Warp Gate can be very powerful. The warp-in time is 5 seconds. The shared cooldown, which lasts for 10 seconds less than the normal build time of the unit, (e.g. a Dark Templar, which normally takes 55 seconds to build, only causes a cool down time of 45 seconds) starts when the unit begins warping in. e.g. if you begin warping in a Dark Templar at 20:00, it will be finished warping in at 20:05, and the Warp Gate will be ready to warp in another unit at 20:45.
Warps In
Abilities
Upgrades
Screenshots
10
200 
200 
