If you get to work and find racial slurs written on the glass door to your office, it's fairly obvious that you are being harassed and discriminated against on the job. It's things like this -- and worse -- that are why we have such extensive anti-discrimination laws today.
However, that does not mean discrimination doesn't happen. It's often just more subtle now than it used to be.
For instance, imagine that an African American worker goes in for an interview. The interviewer is white, but they seem kind enough. They shake hands and spend half an hour talking. Then the interviewer says they'll let the worker know. When the call comes in, they simply say that they decided to go in another direction.
It all appears to be fine. But what if the chief executive officer (CEO) of that company never hires African American workers? What if they always decide to "go another direction?" They may not deny interviews or tell the applicants, but they may have known as soon as the African American worker walked in the door that they wouldn't get the job.
The same thing can happen to people in all sorts of protected classes. Some companies may refuse to hire on a basis of age, gender, religion and other things of this nature. Again, they don't say it or have any offensive policies in writing, but they still practice this subtle discrimination regularly.
If you feel like this is happening to you, it can be complicated and difficult to expose. Make sure you know about all of the legal options you have.