Difference between lexical and bind parameter

Bind parameters are used in where condition.
When u want to pass any value at runtime we use bind parameter as
we use '& 'in sql and pl/sql.
for eg ,
In reports
we give
select empno,ename from emp where deptno =:dno
this :dno acts as bind parameter.
Secondly,
Lexical parameter is used to pass an entire where condition at
runtime.
for eg,
select empno,ename from emp &X
At run time we can pass the entire where condition like
where deptno=30 and sal>3000 etc....