It's no problem to insert and delete cells in your worksheet. When you insert cells, Excel moves the remaining cells in the column or row in accordance with the direction you specify. Deleting cells is the opposite of inserting cells because the remaining cells are shifted to fill in the deleted cell.
Deleting a cell and clearing a cell are two very different actions. Deleting a cell removes the physical cell from the worksheet and forces the remaining cells to fill in the hole. Clearing a cell erases the contents of the cell, but leaves the cell still in the worksheet.