WN7 like all other stats, is a formula that measures how much you contribute to a battle. Damage, kills, cap resets, etc.

What is the difference between WN7 and WN8?

The main difference is that WN7 uses one number for all of your units (but it takes average tank tier into consideration), while with WN8 its possible to calculate players performance on single tank, then aggregate values together using average (not sure).

What is WN8 and WN7 in WOTB?

Both are aggregated metrics trying to evaluate the performance of a player, based on a formula. The formula was tweaked many times, and WN7 was the 7th attempt. It is largely inadequate and obsolete. WN8 was the 8th attempt. It was never completed and remains a beta.

What is WN8 blitz?

In World of tanks Blitz-ian, it is slightly different. WN8 is your overall skill (KDA ratio, Damage per battle, hit%, shot efficiency, etcetera) in a SPECIFIC tank, in comparison with other players in the SPECIFIC tank.

What is a WOT rating?

WOT Efficiency Rating is a collection of data that shows how effective you are on battlefield, your damage and your overall performance in combat. The automatic WOT efficiency calculators allows you to evaluate a combination of factors which show how good is particular WoT player.

Does spotting count for WN8?

As far as I know, spotting and tracking is not included in WN8 calculation.