Yes, the active cell is outline in black.
dfsf
A cell that is outlined in green is normally the second cell referenced in a formula, when you start to edit the formula. It does not have to have any data in it. You could be referring to the active cell, but that is not outlined in green and again it does not have to have anything typed into it.
thin black cross
the active cell
Yes you can.
active cell
At any moment in time, at least one cell has to be selected in Excel. It is known as the active cell. There has to be a focal point so that data or formulas can be typed in. Even when more than one cell is selected, there is only one active cell. Which cell is the active cell can be changed at any time, but there always has to be an active cell. If there isn't then, before you do anything, you would have to make a cell active. Cells are fundamental to Excel so there has to be an active cell at all times.
At any one time you can only be working on one cell in Excel, like when you are typing data. Even if you have many cells selected, only one can actually be used. That cell is the active cell. All other cells are inactive. So an inactive cell is any cell that is not the active cell.
If you select one cell, it will be active. However, if you select multiple cells at once, only one can be the active cell. That is usually the cell you select first.
cell contents
It could be called the current cell.
yes
To format a cell in excel right click on it, then on the thing that pops up click on format cell