The quotation marks at anywhere in the println statement indicate the beginning of a string.
For example, println("hehe") prints out the string "hehe".
If you use the quotation marks at the very beginning and at the very end as well, it would be "x + is here", and the console literally print out "x + is here".
The plus sign is not the same as the plus sign in 3 + 7. It indicates that the value of x will be added to the string "is here"
What we want the console to print out is the value of x, and "is here" right next to it, so the println(x + "is here") would print out "3 is here", instead of "x + is here".