Recently i was trying to do some CSOM coding for a project that requires files to be migrated to SharePoint 365. I created a list in the SharePoint web site and was trying to add new records to the list. I tried to use the "Display Name" for each column from the list in as shown in Diagram 1.
Diagram 1
As you can see from Diagram 2, the line of code that does not work actually makes use of the "Display Name".
Diagram 2
if you try to execute the code you will get the following error.
Diagram 3
In order to get the internal for all the columns, i have to go to the list settings and click on each column and to check the URL for the column internal name. You can see that in Diagram 4.
Diagram 4
The url actually contains the column internal name and you can copy the name from there. The other way which is not covered here is using code to retrieve the internal names.