Dollar signs are very helpful if you know how to use them and quite simply, some tasks would be hell without them.
Dollar signs are used in formulas to lock cell references so that when you copy or drag from one cell to the next your formula doesn’t update.
As an example, say you have this formula in cell A1
if you copy cell A1 and paste it into cell B2 the formula will update to
You have locked the row number 1 with the dollar sign but the D has updated to an E as you pasted the formula one column to the right
You could similarly lock the column by making the formula
=$D$1. You can quickly see how you need dollar signs to save you having to type the formula each time.