What do the icons (key vs steam icon) in review headers mean?

[Rocket Witch]

In response to reply below: why does one type count and the other not?

[MalikQayum]

steam icon means a purchase was made from the steam store, a key icon means the purchase was made on a third party site, steam icon reviews will count towards the review score the key icon will not.

[Darren]

Keys don't count by default in the aggregated score because Developers can generate unlimited numbers of keys for free and do essentially whatever they want with them meaning they can freely provide these keys to people for favourable reviews to skew the numbers.

The Steam purchase on the other hand Steam had to be paid 30% of the purchase price making such an endevour expensive.