Religion and ethics are heavily intermingled for those who are religious, since one's religious beliefs will typically impact ethical issues. Those who practice or believe a specific faith are usually guided by the faith in all areas of the life. This does not mean that religion and ethics are always interlinked, since those who have no specific leaning in matters of faith can still be ethical.
Ethics are the guidelines or personal beliefs by which humans live their lives. Since most religions give instructions by which believers are to base these beliefs, religion and ethics are almost one and the same for those of faith. Christians, for instance, live their lives based on the teachings of the Bible and the Ten Commandments. Other faiths have different written guidelines for living. Most people of faith base every moral decision on the teachings of their particular faith. For instance, many Christians choose to give money to the poor because the Bible says this is good or right.
Although religion and ethics are connected, that doesn't that they can't exist apart from one another. Ethics are also based on teachings one learns from society as a whole. Cultures have basic understandings amongst citizens that people live by. For instance, most people agree that killing and stealing are morally wrong because they cause harm to other people. These beliefs are not automatically based on religion, although most religions also teach against these things, because even those who have no particular faith-based beliefs would agree that these things are wrong.
Ethics are considered to be a personal choice since individuals may have different ideas of what constitutes right or wrong. These matters also vary from culture to culture. Even regions within the same country may have varied ethical beliefs. For instance, in the United States many Southern states are predominantly Christian with corresponding belief systems amongst most residents. California, on the other hand, has many Christian citizens with much more liberal beliefs.
It is a false assumption made by some that religion and ethics must always coincide. Some beliefs seem to be fundamental to most cultures and societies no matter the predominant religious affiliations of the area. So while religion cannot exist independent of ethics, ethics can exist without religion.