Basically, TSF stands for Time-Series Framework, which is the library that underpins all of GPA’s synchrophasor products. <tsfid> is the Point ID of the measurement in openHistorian. <tsfSource> is going to be either the acronym of the historian or the device that the measurement is associated with. These two values make up the measurement key (example: PPA:14), which you have probably seen before. The measurement key is used to identify the measurement in openHistorian’s internal processes.
The rest of the fields you asked about are specific to the DNP3 protocol. I have next to no experience with DNP3 so I lack conceptual understanding and familiarity with terminology. Take the rest of this information with the disclaimer that it was entirely derived through speculation based on my experience with the tools to set up this test system.
<dnpIndex> seems to be a way of identifying an individual signal based on its position in a collection of signals with the same data type. In other words, if you think of each of the map sections as representing a collection for an individual data type (binary, analog, counter, etc.) then the <dnpIndex> would be a zero-based index in that collection. For a real DNP3 device, I imagine that these indexes and their meanings would be defined in the documentation from the vendor.
<localaddr> and <remoteaddr> appear to be sort of like a DNP3 port number, though I really only just set them up to match the link’s source and destination that I configured in the simulated outstation and have not done any experimentation at all with changing them to see what happens. Wikipedia indicates that DNP3 defines an OSI model layer 2 protocol so maybe you could think of them as similar in function to a MAC address.