The active cell is just the current cell - wherever you move to, or click on, in the worksheet. The way to address the active cell is, not surprisingly:
ActiveCell
A cell has lots of properties - a font, value, a formula, background color and so on. Here are some of the more important properties:
ActiveCell.Value - The simple text or number or date of a cell (as it is displayed in the sheet). If the cell contains a formula, then Values displays the results of the formula. For example:
If ActiveCell.Value = "0" Then
ActiveCell.Value = "Zero"
Else
MsgBox "Cell has value: " & ActiveCell.Value
End If
This converts a current cell containing "0" to "zero" and displays the value of current cell if it does not contain zero.
In a similar way, the current cells formula can be determined or set using:
ActiveCell.Formula
The Formula property returns either the formula (for example "=a1 + a2") or, if the cell does not contain a formula, the value.
Here are some more properties:
ActiveCell.NumberFormat
ActiveCell.Font
(for example)
ActiveCell.Font.Bold
ActiveCell.Font.Italic
ActiveCell.Font.Name
ActiveCell.Font.Size