what is printf in bash code example

Example: printf in bash

printf "$your_var1 $your_var2 $(tail -n -1 your.log | grep Word_to_grep ) \n" >> ../opt_done.txt 

# several things, 
# printf with \n new line
# $(tail -n -1 your.log | grep Word_to_grep )  --> is a command, will output whats comes in terminal
			(if final line of the document has "Normal" to grep it will grep, oherwise nothing 
# $your_var1 $your_var2 variables
# >> this is an appending,