There are two types of sonar in recent history. The one that is like the "old days" is called 2D sonar and broadcasts a somewhat inverted cone shaped sound pulse.
The new kid on the block is Imaging. That has a very thin sound pulse front to back and wide to the sides sort of like a CAT scan that hospitals use. That thin pulse produces a somewhat picture like image if what is below.
Side Imaging has two sonar pulses, one broadcasts to the left and the other broadcasts to the right. That will produce what looks like this rock pile with lots of crappie around:
Down Imaging is more downward focused but is still Imaging and looks like this tree on the bottom:
This screen shot shows the difference between how 2D sonar and Down Imaging represents a brush pile:
Humminbird has Sonar models that are 2D sonar, DI models that have Down Imaging and 2D sonar, and SI models that have Side Imaging, Down Imaging and 2D sonar.
In the Helix 10 series, all of them have GPS/Mapping.
The version you choose includes a transducer that will produce the sonar technology/s that the unit is capable of.