Column histogram information
When you are previewing a table on the dataset overview page, if you click Switch to column overview in the lower right corner of the table, you'll see information on the format and values in that column. Selecting one the lines brings up the information for that particular column. When a histogram is displayed you can hover over any point on the histogram for information about that value. By default columns are sorted by frequency but they can also can be sorted by value. Other information about the column captured in the overview includes:
number of distinct values
number of empty and non-empty cells
minimum, maximum and mean length of values
the name of the table the column is in
the unique column identifier