What's the difference between Range.Item and Range.Cells?

The best way to understand this is via the below example

When .Item and .Cells are used with respect to a range then, YES, they are same. For example

Sub Sample()
    Dim rRange As Range
    Set rRange = ThisWorkbook.ActiveSheet.Range("B1:C10")

    With rRange
        Debug.Print .Item(1, 3).Address '<~~ $D$1
        Debug.Print .Cells(1, 3).Address '<~~ $D$1
    End With
End Sub

In the above they both depict the address of the cell in that Range

They are different when Cells() is used independently of a range.

Sub Sample()
    Dim rRange As Range
    Set rRange = ThisWorkbook.ActiveSheet.Range("B1:C10")

    With rRange
        Debug.Print .Item(1, 3).Address  '<~~ $D$1
        '~~> DOT before Cells missing
        Debug.Print Cells(1, 3).Address  '<~~ $C$1
    End With
End Sub

In the above .Item depicts the address of the cell in that Range, where as Cells depicts the address of the cell in the ActiveSheet