In the context of a function, a GROUP BY clause, an ORDER BY clause, an expression, or a search condition, a column name refers to values of a column in some target table or view in a DELETE or UPDATE statement or table-reference in a FROM clause.
The tables, views, and table-references 1 that might contain the column are called the object tables of the context. Two or more object tables might contain columns with the same name. One reason for qualifying a column name is to designate the object from which the column comes. For information about avoiding ambiguity between SQL parameters and variables and column names, see References to SQL parameters and SQL variables.
A nested table expression which is preceded by a LATERAL or TABLE keyword will consider table-references that precede it in the FROM clause as object tables. The table-references that follow the nested table expression are not considered as object tables.