Functionality of UBound in For loop

[Vicasso]

What is the functionality of UBound in for loop for the below code.

x = wsPlan.Range("A1").CurrentRegion.Value
Set Plan = CreateObject("Scripting.Dictionary")


For i = 3 To UBound(x, 1)
For j = 2 To UBound(x, 2)
Plan.Item(x(1, j) & x(2, j) & x(i, 1)) = x(i, j)
Next j
Next i

 

[Fluff]

It returns the Upper bound value of the array, so if the array "x" has 100 rows & 10 columns the 1st Ubound will return 100 & the 2nd will return 10.