What is this curve ??

What is the meaning of this curve shown in figure.
It is in our profile pages below rating graph inside date range selection slider.
How to interpret this curve going up and down ?

Activity it appears... like a roller coaster.

Can some one please give a detaild explanation about the curve ?

This curve corresponds to a Bullet curve which is usually not so smooth. It shows your progress in Bullet games.

it means your skill dropped in that curved time period

This is no Bullet curve.

Bullet curve or not ? confused ??

Yes, it is the bullet curve.
Look on the profile page of players who doesn't play bullet, there is nothing in this area.
And if you pay attention, the curve match with the up & downs of the bullet rating.

Thank you !!!