Prejudice is an irrational feeling of dislike for a person or group of persons, usually based on stereotype. Virtually everyone feels some sort of prejudice, whether it’s for an ethnic group, or for a religious group, or for a type of person like blondes or fat people or tall people. The important thing is they just don’t like them — in short, prejudice is a feeling, a belief. You can be prejudiced, but still be a fair person if you’re careful not to act on your irrational dislike.
Discrimination takes place the moment a person acts on prejudice. This describes those moments when one individual decides not to give another individual a job because of, say, their race or their religious orientation. Or even because of their looks (there’s a lot of hiring discrimination against “unattractive” women, for example). You can discriminate, individually, against any person or group, if you’re in a position of power over the person you want to discriminate against. White people can discriminate against black people, and black people can discriminate against white people if, for example, one is the interviewer and the other is the person being interviewed.
Racism, however, describes patterns of discrimination that are institutionalized as “normal” throughout an entire culture. It’s based on an ideological belief that one “race” is somehow better than another “race”. It’s not one person discriminating at this point, but a whole population operating in a social structure that actually makes it difficult for a person not to discriminate.
Now to “Reverse Racism.” It’s crucial to maintain the distinction between the above three terms, because otherwise white people tend to redefine “Discrimination” as “Racism”. Their main argument is that because both blacks and white can discriminate against each other, that “Reverse Racism” is possible. But the truth of the matter is that black people: 1) have far less opportunity to discriminate against whites than whites have to discriminate against blacks, overall; and 2) black people lack a system of institutionalized support that protect them when they discriminate against whites.
"Reverse Racism" would only describe a society in which all the rules and roles were turned upside down. That has not happened in the U.S., however much white right wing ideologues want to complain that they’re being victimized by the few points of equality that minorities and women have managed to claim. White people who complain about "Reverse Racism" are actually complaining about being denied their privileges, rather than being denied their rights. They feel entitled to be hired and not to be discriminated against, even though the norm is white people discriminating against blacks. If, in a rare instance, a black employer discriminates against a white job applicant, that’s not "reverse" anything — it’s simple discrimination. It’s to be condemned on principle, but it’s not evidence of some systematic program by which whites are being deprived of their rights."