Frequency conversion provides a basic way to convert the index in a time series to another frequency. Data in the new time series is aligned with the old data and can result in many NaN values. This can be partially solved using a fill method, but that is limited in its capabilities to fill with appropriate information.
Resampling differs in that it does not perform a pure alignment. The values placed in the new series can use the same forward and reverse fill options, but they can also be specified using other pandas-provided algorithms or with your own functions.
To demonstrate resampling, we will use the following time series, which represents a random walk of values over a 5-day period: