Dialog utility

Hi,
I am new to shell scripting, started learning script before one month. I can't understand the below script.

dialog --title "Inputbox - To take input from you" --backtitle "Linux Shell\
 Script Tutorial" --inputbox "Enter your name please" 8 60 2>/tmp/input.$$ 

In this script they are redirecting the inputbox value to temporary file. why 2 is used here 2>/tmp/input.$$

Please help me to understand the script

Please use code tags as required by forum rules!

That's redirecting stderr implicitely using file descriptor 2 (cf. man bash or other shell)