How to remove this please?

[NJ0101]

suddenly this graph pops up all the time in my editing. How to remove this please? What is this? Thats the different color graph that moves up & down next in the back arrow tab. Top side with the clock. Thank you. 

 

 

[JohanElzenga · Accepted solution]

That is the histogram. If you do not want to see it then tab (twice, the first tab will change it to info) with two fingers.