In Unreal, Data Tables are a method of importing and using custom game data exported from a spreadsheet application. To do this, you first ensure that your spreadsheet follows some guidelines for format; additionally, you write a C++ struct that contains the data for one row of the spreadsheet. Then, you export a CSV file and select your C++ struct as the data type for that file.
Your spreadsheet must follow some simple rules in order to correctly export to Unreal.
The very first cell must remain blank. After this, the first row will contain the names of the fields. These will be the same as the variable names in your C++ struct later, so do not use spaces or other special characters.
The first column will contain the lookup key for each entry. That is, if the first cell of the first item in this spreadsheet is 1, then in Unreal, you would use 1 to find that entry. This must be unique for every row.
Then, the following columns...