Shading cells once info on a column changes

Good afternoon,

My initial problem was alternating the shade of cells once there is a change in value based on information on 1 column.

Fortouantely I have a formula that can do this when i use conditional formating; however, I am at a loss on how it works. Below is the formula

=MOD(SUMPRODUCT(--(($A$1:INDIRECT(ADDRESS(ROW()-1,1,3,1))=$A$2:INDIRECT(ADDRESS(ROW(),1,3,1)))=FALSE)),2)

Question:

How does it work?

In particular, in the sumproduct function, there are two "-". Additionally, why is it assigning a false value? What does this code do: (--(($A$1:INDIRECT(ADDRESS(ROW()-1,1,3,1))=$A$2:INDIRECT(ADDRESS(ROW(),1,3,1)))=FALSE)?

bump..........