Hello Palak, MaxInstances is the no. of browser instances (of same versions) that can run on the remote machine, as shown in following commands:
It means we can run three instances of both Firefox and IE at the same time. So, a total of six different browsers (FireFox & IE) could run in parallel.
While MaxSession shows how many browsers, independent of the type & version, can run concurrently on the remote machine. It supersedes the “MaxInstances” setting. From above command, if the value of “maxSession” is one, then no more than a single browser would run. While its value is two, then any of these combinations (2FF, 2IE, 1FF+1IE) can run at a time.