[ This program prints "Hello World!" and a newline to the screen, its
length is 106 active command characters. [It is not the shortest.]

This loop is an "initial comment loop", a simple way of adding a comment
to a BF program such that you don't have to worry about any command
characters. Any ".", ",", "+", "-", "<" and ">" characters are simply
ignored, the "[" and "]" characters just have to be balanced. This
loop and the commands it contains are ignored because the current cell
defaults to a value of 0; the 0 value causes this loop to be skipped.

from https://en.wikipedia.org/wiki/Brainfuck#Hello_World! ]
++++++++	Set Cell #0 to 8
[
>++++		Add 4 to Cell #1; this will always set Cell #1 to 4
[		as the cell will be cleared by the loop
>++		Add 2 to Cell #2
>+++		Add 3 to Cell #3
>+++		Add 3 to Cell #4
>+		Add 1 to Cell #5
<<<<-		Decrement the loop counter in Cell #1
]		Loop until Cell #1 is zero; number of iterations is 4
>+		Add 1 to Cell #2
>+		Add 1 to Cell #3
>-		Subtract 1 from Cell #4
>>+		Add 1 to Cell #6
[<]		Move back to the first zero cell you find; this will
		be Cell #1 which was cleared by the previous loop
<-		Decrement the loop Counter in Cell #0
]		Loop until Cell #0 is zero; number of iterations is 8

The result of this is:
Cell no :   0   1   2   3   4   5   6
Contents:   0   0  72 104  88  32   8
Pointer :   ^

>>.			Cell #2 has value 72 which is 'H'
>---.			Subtract 3 from Cell #3 to get 101 which is 'e'
+++++++..+++.		Likewise for 'llo' from Cell #3
>>.			Cell #5 is 32 for the space
<-.			Subtract 1 from Cell #4 for 87 to give a 'W'
<.			Cell #3 was set to 'o' from the end of 'Hello'
+++.------.--------.	Cell #3 for 'rl' and 'd'
>>+.			Add 1 to Cell #5 gives us an exclamation point
>++.			And finally a newline from Cell #6