Avatar Project (XCOM2)
The Avatar Project is the end goal of the aliens. Figuring out what it is and stopping it comprises most of the plot of the game.
On the Hologlobe, the Avatar Project, once revealed, will take a spot at the top center of the display, where its progress is represented by a bar of 12 paritions, or 'blocks'. This bar will fill when the Aliens make progress on the project, and be drained when XCOM makes progress against the project.
If the aliens manage to fill all 12 blocks, the display is replaced by a countdown timer. If this countdown reaches zero, XCOM will be defeated and the game will end. The timer can be halted(and returned to the normal display) by reducing Avatar progress before the countdown ends.
Reducing Avatar Progress
Each Alien Facility on the map, as well as the Avatar Progress master counter in the Pacific Ocean, will have a number of blocks under it. Those are the blocks which that facility devotes to the Avatar project; destroying an alien facility will eliminate all progress the aliens are getting from that facility.
Furthermore, you can reduce Avatar progress simply by progressing through the plot. The following actions reduce Avatar progress by the stated amounts.
- Steal Blacksite Vial: 1 block
- Steal Forge Stasis Suit: 2 blocks
- Skulljack an Advent officer and kill the resulting Codex: 1 block
- Steal the Psionic Gate: 2 blocks
- Skulljack a Codex and kill the resulting Avatar: 3 blocks
- Completing a covert mission to reduce the Avatar Progress: 2 blocks (requires War of the Chosen)
There seems to be a small amount of micro-managing possible if a Reduction action is completed shortly before timed Avatar progression is made during scanning: if a save shortly before the notification is reloaded, and one of the above actions is possible and completed, it resets the internal timer count, retroactively buying you extra time. In other words: if it takes X amount of time for the aliens to fill a pip on the counter, and you unlock a reductive action in 50% of that time, wait until it's 90% complete before actually doing it, as it will still take X amount of time again for the aliens to catch back up again, making them waste 40% of X amount of time. This may not always work, however.