In the Sanderling API Explorer, at the top level of the tree are three nodes with similar names:
MemoryMeasurementMemoryMeasurementParsedMemoryMeasurementAccu
Of those three, you only need MemoryMeasurement to read information from the EVE Online client.
The other ones (Parsed and Accu) are derived from MemoryMeasurement, without any additional information from the EVE Online client. The properties MemoryMeasurementParsed and MemoryMeasurementAccu are an accumulation of popular frequently used derivations of information available in MemoryMeasurement.
Their purpose is to make it easier for people to use popular derivations, but you can always program your own instead.
So what are the differences between Parsed and Accu?
MemoryMeasurementParsed
MemoryMeasurementParsed is completely derived from the last MemoryMeasurement and this derivation process is referred to as ‘parsing’, hence the appendix in the symbol.
Typical work done in parsing is translating text to a number. An example of this is are distances shown in the overview window. A text like “11 km” is translated to 11000 meters, while a text of “11 m” is translated to 11 meters. The translation enables you to use these values in arithmetic operations such as checking if a distance is smaller then a given threshold.
MemoryMeasurementAccu
The MemoryMeasurementAccu is an accumulation of data from all MemoryMeasurement, not only the last one but also past ones.
A good example of remembering information from the past is the tooltips shown when you hover your mouse cursor over a ship module. When the bot wants to know the maximal working distance of a module, it can look up this information in the tooltip. Since the tooltip is not always visible, we want to remember a tooltip which was displayed sometime in the past.