Difference Between Lexical and Bind Variable

Bind references are used to replace a single value in SQL or PL/SQL. Specifically, bind references may be used to replace expressions in SELECT, WHERE, GROUP BY, ORDER BY, HAVING,CONNECT BY, and START WITH clauses of queries. Binds may not be referenced in the FROM clause.
An example is:
SELECT Col1,Col2
FROM XX_table
WHERE Col1 = :P_col1

Lexical references are placeholders for text that you embed in a SELECT statement. You can use lexical references to replace the clauses appearing after SELECT, FROM, WHERE, GROUP BY , ORDER BY , HAVING, CONNECT BY, and START WITH. You cannot make lexical references in PL/SQL. Before you reference a lexical parameter in a query you must have predefined the parameter and given it an initial value.
An example is:
SELECT Col1,Col2
FROM &ATABLE