I have often found bisphosphate compounds ( e.g. RuBP, RuBisCO, 2,3-BPGA etc.) and diphosphate compounds (e.g. ADP, GDP etc.) in biochemistry. They are commonly seen and are important compounds in both animals and plants but what is the basic difference between a bisphosphate and a diphosphate?
As you can see in the above structure of ADP(Adenosine di-phosphate), the two phosphate groups in the compound are directly attached to one another. So it is named as di-phosphate. [Source] You can see this table for more examples.
In this structure of RuBP(Ribulose-1,5-bisphosphate), the two phosphate groups in the compound are not directly attached to one another, they are attached to first and fifth carbon, meaning they are attached to different atoms. Therefore, it is named as bis-phosphate. [Source](2nd comment)