To talk about discrimination, the employer does not have to discriminate against all employers based on a given characteristic. Discrimination does not have to be a conscious and intentional act.
Direct discrimination occurs when an employee is treated less favourably than other employees for one or more of the discriminatory premises.
Indirect discrimination is a result of a provision, criteria or action that favours one group and/or hinders another in hiring, discharge, conditions of employment, promotion and access to professional training. It affects all or most of the workes bearing some characteristics, e.g. when the job advertisement indicates that women are preferred to work.
We can’t conclude indirect discrimination when the employer’s decision is objectively justified by the legitimate aim and the means of achieving that aim are appropriate and necessary.