Oracle default it will get better plan from using cost based optimizer based on Table indexs, Data distribution and statistics. Some time even you can check is there any better plan other than this in OEM or SQLT for that query. if you see any better execution plan you can select that SQL profile and attach to that SQL from next onwords the query will execute with the better SQL profile plan we attached to it.
But based on today statistics, code, data distribution and indexes this is the better plan. In feature if any of the this changes like big data change or indexs or statistics or distribution changes our sql profile might not be the best then oracle automatically disable this profile and use the best plan give my oracle.