This code fills SOME cells in rows 3:32 with the corresponding values
of another range, which was named Picked.
The function Range("G2").Offset(1,3) returns a reference to a cell 1
row below and three columns to the right. Your code snippet does not
show what is the value of variable ModelCounter, so I don;t know in
which column you offset.
The loop

For i = 1 to 30
....
Next

makes i get progressively the values from 1 to 30. Whatever appears
inside the loop will be executed 30 times, with i each time having been
incremented by 1.

Similarly, Range("Picked").Cells(i) will get one more cell from the
range called Picked.

HTH
Kostis Vezerides