Normal: Standard and most popular representation of schematic symbol
ALT_1 (IEEE view): Symbol representation in a way that is more graphical in explaining what the purpose of each pin is. For connectors and most discretes (as we use these views) it is simply an alternate view for people to use depending on the situation. For instance connectors can be generally an input, an output or neither. Resistors can be vertical or horizontal.
ALT_2 (demorgan): Demorgan is a name for an equivalent Gate structure. so for instance an AND gate and an OR gate can be represented by its Demorgan equivalent of a NOR gate.
Sometimes a device is fractured into multiple symbols (often for high pin count parts). If that is the case, you can preview the different symbols that make up the device by selecting them in this drop down.
(not all views will be available for every part)
Basic: Our standard footprint view showing, contact area, pin number, top, top assembly
Detailed: Additional info to help you evaluate the part and the footprint including: dimension, silkscreen, soldermask, and solderpaste
PinDetail: Highlights the pin to pad contact area dimensions
Displays min/typ/max pad sizes for footprint per IPC specification (not all sizes will be available for every part)