Geography is just a crap load of excel tables put together in a pretty picture.
The point is at its simplest a table with and a X, Y.
Want to add a line or polygon… its a bunch of X, Y points put together.
Of course the more useful data will have additional attributes… name, numbers of some type, maybe even a unique identifier like a name.
Excel tables save by default as an xls. file. These files aren’t the greatest for putting into a GIS system since they can have more than one tab. Additional and better options include csv. or txt. files that only allow one tab and leave out a lot of the more complex excel table junk.
Why are spreadsheets so important? Very little data is produced in map ready form. The census has thousands of useful datasheets available to them but very little come prepacked as geospatial files.
In summary, a geographer who doesn’t know how to use excel is not a geographer.