Which method to use to remove trend from time series?

Question

From what I understand, differencing is necessary to remove the trend and seasonality of a time series. So I assumed it basically does the same thing as signal.detrend from the scipy library.

But I tried differencing and then, separately, used signal.detrend and my time series looked completely different.

Original:

Differencing:

Imported libraries:

The x axis represents months and the y axis is sales. The colours on the first two charts just represent three different years.