Calculating voltage drop and current use of an IC
Vdd is the power supply voltage.

Vin is the signal input voltage, and Vout is the signal output voltage.

Ioh and Iol are the currents that an output pin can sink or source.  They are not directly related to the current the chip draws from the power supply.

Vih is the minimum input voltage that will be recognised as a logic High

Vil is the maximum input voltage that will be recognised as a logic Low.

Vol and Voh are the maximum and minimum output voltages for Low and High logic levels at the specified output currents.