The four hetero types are as follows:
Type I - different components in one package (PCB Decal) an (old) example of this would be the MMC1488 RS232 driver comprising one inverter and three 2-input NAND gates (see the delivered Starter Library for this part).
Type II - the same logical components in a package but on one symbol you show explicit power connections, for example TL074C Op Amp where you use three gates without power pins and one gate with power pins so they can be wired up in the schematic - you package three non-power pin symbols with one power pin symbol to ensure the physical component has power on the PCB.
Type III - This is a split IC where you have multiple different logical gates with different pin counts making up the part.
Type IV - A component that has two or more logical representations for the same part - for example a 244 Octal buffer using one symbol to reperesent all eight buffers and one symbol representing one half of the package, two symbols making up one part.
The hetero types are explained in the Knowledge Base article KB Article ID# MG583318 on SupportCenter.