Doc,
Most of the time these values can be the same, and we've considered simplifying the UI to reflect that.
The "Column" field is what you want to show in the query builder -- you can regard that as the "friendly name" -- something that's easy to understand based on its name.
The "Alias" field is the name that's assigned via the SQL syntax, and you might want that to be different to make the syntax more readable or easier to maintain if you use the SQL as part of another SAS program.
Chris