1. Mental abuse. Relationships should help you feel good, and love yourself. Many people mentally abuse their girlfriends by telling them things like they are ugly, or that no one else could ever love them. This kind of abuse usually results in a shattering of self-esteem. The woman often can't leave her abuser because she feels worthless, and that no one else would ever love or appreciate her.
If you or someone you know suffers from this kind of abuse, trying to talk them into leaving is fruitless. The only way to help someone suffering from mental abuse is to help them build their esteem, and feel like they are of value. Once they like themselves, they will remove themselves from a situation where their significant other is degrading to them.
2. Physical abuse. This kind of abuse seems to be self-explanatory, but in many cases it is done in a subtle, or justifiable way. "Accidents", or a "loss of control" are blamed for the physical abuse, and the abuser is absolved of responsibility. The person being physically abused often blames himself or herself. If they had not forgotten to do what he asked, he would not have gotten mad and hit me. If I was smarter, prettier, better in bed, he would not get as angry with me. These kinds of thoughts are very common, and very destructive. This is why physical abusers have the power. People outside of the abuse often do not understand how the person would put up with it.
However, it is never as simple as that. They might feel they owe them something. They may feel that they can't do better. The victims of physical abuse usually feel indebted to their abuser for some service rendered in the past. They often have too low of esteem to walk away, or are afraid of the consequences.If you or someone you know suffers from physical abuse, it is critical that you are supportive, that you help them feel safe and welcome should they need a refuse. Threatening them will no work, as that is what the abuser does.
Abuse is very serious, and it comes in many forms, sexual abuse, emotional abuse, physical abuse, mental abuse. The list goes on. Most victims of abuse have low self esteem and have been convinced that they somehow deserve the treatment. So, to help them, help their esteem.