What does Alpha Strike mean

VOD is Video On Demand. On this context, it means a video that is taken from the screen of an observer or from the players themselves (those are called FPVOD-First Person VOD). The video is taken by softwares like FRAPS, in most of the cases. They usually have audio commentary from "experts" in the game, but this is not required.

VODs are used usually when the replay is not available, i.e: in Korean professional league games.

A timing push involves making an attack at a certain point in your build order, such that the attack coincides with the completion of a researched upgrade, or a certain mass of units.

For example: you might see a Terran Bio timing push, where the Terran player moves his forces out such that Stimpack technology will have just finished as they reach the enemy forces.

Also applies to Weapon / Armor upgrades. Since the Weapon / Armor upgrades often completely cancel each other out, it's best to start fights when you have the upgrade, and your opponent does not. If you wait too long, your opponent (if they know what they're doing) will complete their own counter-research, and your advantage will be lost.

Hence, timing push; Timing an attack such that it occurs when you have the momentary advantage.