请老师详细解释一下这组代码

三票

Sub Match_1()
Dim t
Dim Arr, a
Dim Brr, b
Dim Crr, c
t = Timer
With Sheet1
Arr = .Cells(1, 2).CurrentRegion
Brr = .Cells(1, 6).CurrentRegion
ReDim Crr(1 To UBound(Arr) * UBound(Brr), 1 To 5)
a = 1: b = 1: c = 0
Do While a < UBound(Arr)
    b = 1
    Do While b < UBound(Brr)
        If Arr(a, 3) = Brr(b, 1) Then
            c = c + 1
            Crr(c, 1) = Arr(a, 1): Crr(c, 2) = Arr(a, 2): Crr(c, 3) = Arr(a, 3)
            Crr(c, 4) = Brr(b, 2): Crr(c, 5) = Brr(b, 3)
        End If
        b = b + 1
    Loop
    a = a + 1
Loop
.Columns("J:N").ClearContents
.Cells(1, 10).Resize(c, 5) = Crr
End With
MsgBox (Timer - t)
End Sub