ADJGINC is a person level variable that reports an individual’s total gross (pre-tax) income from taxable sources minus certain items (such as individual retirement plan contributions, alimoney, medical savings, business expense accounts, etc.)
The difference between this variable and FTOTVAL and HHINCOME is described in my answer to your previous question. Also note, most information regarding the differences between variables is available online on each variable’s description tab.
The key difference between each of these variables is ADJINC is a person-level variable and FTOTVAL and HHINCOME are both household-level variables. Importantly, however, FTOTVAL reports aggregated income totals based on the US Census’ definition of “family”, while HHICOME is based on a straitforward, yet ridged, definition of “household”.