Gross salary means the salary which you have agreed to be paid to an employee. It is that salary which is considered for deduction when he takes a leave without pay or it is that salary which is paid if he takes leave with pay. Very simple, how is average salary per day calculated? It is by dividing the gross salary by the number of days in the month. Yes, that gross salary is the salary as per contract of employment.
Ex gratia is not a monthly payment but t is paid once in a year or in six months period. Therefore, this is not part of salary. At the same time, suppose you have offered a remuneration,like, Rs 30000 as salary and Rs 5000 every month as exgratia. Here the amount of ex gratia is fixed and is specific amount and is not variable depending upon any future happening like production, sales, performance etc. In such cases, the ex gratia will also become part of contract of employment and will be assessed as salary.
Under ESI, washing allowance paid to employees who are given uniform by the company is excluded from wages. At the same time, for provident fund HRA is excluded. But that does not mean that you can pay any amount as HRA and escape from payment of PF. Only HRA which is paid addition to salary to those who live in rented houses can be excluded. A similar discussion was taken place in some other thread in this form itself. Please check that also.
In any case the employer's liability to contribute to PF can be restricted to 12% of Rs 15000. Rs 15000 is a very small amount and as such the employers who bifurcate this 15000 into small compartments with a view to reducing their PF contribution should be taking PF only as a statutory requirements and not employee friendly. It is very unfortunate that the HR people are still asking the same question which all are the components which can be excluded for PF contribution, just to make the employers happy!