It's the sign for the respective rating of the german rating board "USK". Not more or less :3
And that yellow sign stands for ages six and up - that would be "everyone" as an ESRB rating, eh? ._.
There are also white signs, meaning those games are suitable for anyone. - Ages 0 and up.
Then we have the dark green sign which stands for ages 12 and up - Which would be a "teen" rating
A blue sign is for ages 16 and up and is the equivalent to the "mature" rating.
And last but not least there is the red sign - 18+ aka adults only.
Uhm, yeah, whatever, i hope it helped. :q
*scuffles into his bed* *yawn* G'night.