Oracle SQL - Difference between AND & OR operators

Question

what is the difference between AND and OR Operators?

In the online class shows that AND displays a combination of 2 different conditions whats confusing is OR does the same thing, here is an example:

select employee_id , first_name,job_id,salary

FROM employees

where department_id = 10 

OR Department_ID = 20 

AND job_id in ('FT_MGR','AC_MGR');

Answer 1

AND operator mean both (department_id = 10) is TRUE also (Department_ID = 20 ) is TRUE, result is TRUE

OR operator mean either (department_id = 10) is TRUE or (Department_ID = 20 ) is TRUE, result is TRUE