number of active users

Hi,

I am new to gatling…can any one please explain the number of active sessions in the reports…And what is active sessions…and In that it contains concurrent users or simultaneous users???please explain with example…

And what is concurrent users???

And what is simultaneous users???

And how to calculate these users in gatling

Thnaks

http://gatling.io/docs/2.0.2/general/reports.html

Thanks…But please explain in detail with example…And I also want details about in that active sessions what are the types of users???will it take concurrent users or simultaneous users?why it is showing less number of active users even though if we give more number of users???