Its pretty simple, I think. . .
First of all, don't let the word Grid get to you. Remember, technically a grid can be 1 row by 15 columns.
Think of it as a straight line of boats just behind the pace boat as it has always been. The "pole" position would be the closest boat to the inside of the upcoming turn buoy. This is often (but not always) a coveted position, and hence is being considered to be an advantage. The winner of a race will have to start the following race on the far outside of the line, thus having the furthest distance to travel to the upcoming turn buoy. The boat finishing last in the previous race would be awarded the #1 position, or the "pole".
<1> <2> <3> <4> <5> <6> <7> etc, etc.
Don't confuse this type of start, with a 2x2 grid following a full course yellow flag. Remember too, that if the inside of the course doesn't allow, the pace boat may actually be just outside of starting grid, rather than on the inside. It happened maybe twice last year.
Hope this helps.