Why are these 2 queries giving different outputs?

Query no 1:-

SELECT COUNT(ENAME)
FROM EMP
WHERE 
 JOB IN 'MANAGER' 
 OR JOB IN 'ANALYST' 
 AND SAL IN (
    SELECT SAL + NVL (COMM,0)
    FROM EMP
    WHERE SAL LIKE '%0')
GROUP BY JOB;

The Query 1 gives me the following output:-

COUNT(ENAME)
------------
           3
           2

Query no 2:-

 SELECT COUNT(ENAME)
 FROM EMP
 WHERE 
   JOB = ANY (
       SELECT JOB
       FROM EMP
       WHERE JOB IN ('MANAGER', 'ANALYST') 
     )
   AND SAL IN (
       SELECT SAL + NVL (COMM,0)
       FROM EMP
       WHERE SAL LIKE '%0'
     )
 GROUP BY JOB;

The Query 2 gives me the following output:-

COUNT(ENAME)
------------
           2
           2

Answer

Summary: The AND operator has higher precedence than the OR operator. To fix it, use brackets around the OR expression.

---

AND has higher precedence than OR so your first query is the equivalent of (with added brackets and indentation to emphasise the precedence):

SELECT COUNT(ENAME)
FROM   EMP
WHERE  JOB IN 'MANAGER' 
OR     (     JOB IN 'ANALYST' 
         AND SAL IN (
               SELECT SAL + NVL (COMM,0)
               FROM   EMP
               WHERE SAL LIKE '%0'
             )
       )
GROUP BY JOB;

So you are finding either: managers with any salary; or analysts whose salary equals the salary plus commission of any other employee.

Your second query is the equivalent of:

SELECT COUNT(ENAME)
FROM   EMP
WHERE  (    JOB IN 'MANAGER' 
         OR JOB IN 'ANALYST'
       )
AND    SAL IN (
         SELECT SAL + NVL (COMM,0)
         FROM EMP
         WHERE SAL LIKE '%0'
       )
GROUP BY JOB;

Which finds: any employee who is either a manager or an analyst and whose salary equals the salary plus commission of any other employee.

---

You could rewrite your first query to:

SELECT COUNT(ENAME)
FROM   EMP
WHERE  JOB IN ('MANAGER', 'ANALYST')
AND    SAL IN (
         SELECT SAL + NVL (COMM,0)
         FROM   EMP
         WHERE SAL LIKE '%0'
       )
GROUP BY JOB;