Throughout you will see some of the following: (N) means normal mode, or rather the first play through, (H) means hard mode, or rather the second play through, (SH) means super-hard mode, or rather the third play through.  Whenever Higsby's is present, it means that either you can purchase the chip or order the chip.  By Traders, it can include the 3 chip trader at Higsby's Shop, the 10 chip trader in ElecTown, or even the 10 chip trader in Netopia (perhaps even a bug-frag trader/dealer).  Also, GMDs will mean Green Mystery Data present in the world and in battles, BMDs will mean Blue Mystery Data, and lastly PMDs mean Purple Mystery Data which need to be opened with an Unlocker (sub-chip).