Literal meaning - Ad hominem are Latin words, which mean - 'to the man' or 'against the man.

Let's go through few examples to get a better understanding of ad hominem.

1. Two people are arguing about something. One of them unnecessarily brings in the other's religious beliefs, and says he has such views on this topic because perhaps, if he wasn't a part of the religious group he belongs to, he would've had a different opinion.
   
   Explanation: Now here, bringing in the person's personal beliefs was not required, as this is a clear attack on the person, and not on the argument that had nothing to do with the comment made.
2. A woman and a man are having a discussion about issues related to women rights. When the woman responds to him saying that, his opinion on women rights didn't matter, and he wouldn't understand what it is to be a woman, because he's not one.
   
   Explanation: Here, she makes a personal attack on his gender, maybe because she didn't have any proper explanation or the required answer to what the man said!
3. Two young men are debating on a topic, when the elder one comments on the younger, "You are clearly too young to understand or speak on a topic like this."
   
   Explanation: The victim did not deserve such kind of a comment just because he was younger than the other. Being small by age doesn't define the level of intelligence or thinking of a person.

Yes, definitely. Ad hominem of any kind is a fallacy, because it causes personal harm to people when there is no need of it.

A common example we all might have experienced at some point of time - Two friends are fighting over something, and you try to interfere to solve their problem. You support the friend who you think is talking sense, but the other immediately comments on you, that you would obviously support your other friend because you've always been more close to him, or you always think she's (the person attacking you personally) wrong.

Here, wavering from the main problem, this topic now takes a very different turn. It all comes down to you now, because you support only one of them or the wrong person simply wouldn't agree upon anything you say, since she has already called you biased. Reasons can be, maybe she knew she was wrong, but still in an effort to prove herself right she puts the blame on you and tries changing the topic, or maybe you really are closer to the friend who is correct, but right now you totally support what you feel is really correct.

In such situations the unnecessary accusations may be false or true, but it still would be considered a fallacy because it's irrelevant to the topic.



Abusive ad hominem - This would include verbal personal attacks on the character of the person, in an argument that has nothing to do with the person's traits, making it a logical fallacy. If verbal abuse is done when not in an argument, it will not be considered as ad hominem.

examples:

1. A - You at least need to know the basics before you start its implementation!
   B - What do you know about anything you village idiot? Just shut your mouth and let me do my work!
   
   By calling A a village idiot, B has attacked A personally, without even listening to the point he was trying to make.
2. You are just an ignorant stupid girl, and i don't believe anything that you are saying!

A plain abusive sentence which cannot be considered as an ad hominem would be - "Your face is what i can't stand. If you can understand what I'm saying, just please get the hell out of my way!" Since, there is no topic of discussion or debate here, where one is to be proved right, this cannot be considered as ad hominem.

Tu quoque - Tu quoque is also Latin, literally meaning "You also". In this type when A criticizes B, of something he himself (A) had done in the past, and if B knows about it, it gives him a perfect chance to accuse him back and hence prove him wrong. In such a case, B wouldn't listen to A, thinking A is just a hypocrite. Where this case of hypocrisy might really be true, but there are chances of an honest advice or suggestion from stopping the other to do something wrong that the adviser has already done.
This is considered a fallacy, because whatever the counter-accusation proves, it still doesn't prove if the person at fault is right or wrong and is irrelevant to the case.

examples:
In response to a criticism -
A criticizes B for taking drugs and tells him of the dire consequences, but B knows that A has been or is still an addict of it and points it out in the argument. This is tu quoque. But here, A might be giving B an advice from his own experiences.

In response to support -
A - "Isn't it cleaner and fresher in this area?"
B - "Yea sure it is, so, why don't you just settle here!"

This is when, you support a claim, but don't really like it so much.

Circumstantial - Circumstantial ad hominem is when a person is personally attacked on the basis of his circumstances or position or whom he is related to.

examples:

1. A can't be right because of the surroundings he has been in. He will always think the opposite!
   
   Here, even if A is making a correct argument, B is making him look wrong judging him by his surroundings.
2. Priest - Abortion is a wrong thing to do. It is a sin.
   Woman - Yeah why wouldn't you say that? What do you know anything about taking up responsibilities of a child?
   
   Now here, just because he is a priest he has been blamed on his circumstances.

Guilt by association - In this type, a person making a claim is associated by people supporting it (if they have a negative influence), and is then judged negative on the basis of that.

examples:

1. A makes a right claim, but is contacted by a non-social negative group recently, on some different matter. A is now judged as a person who is associated with that group and hence he cannot be right about his claim.
2. A speaks against smoking and about its consequences. B criticizes him of being surrounded by friends who are smokers, and so A cannot be right about what he speaks.

Ad feminam - This type as the name suggests is the personal attacks made on women on the basis of gender. Just because she is a woman, her claims cannot be correct - attitude.