-- As the name suggests, DESCRIBE is used to describe something. Since in database we have tables, that’s why we use DESCRIBE or DESC(both are same) command to describe the structure of a table.
Syntax:

DESCRIBE one;
  OR
DESC one;
-- Note : We can use either DESCRIBE or DESC(both are Case Insensitive).

-- Suppose our table whose name is one has 3 columns named FIRST_NAME, LAST_NAME and SALARY and all are of can contain null values.