Difference between cold war and civil war?

A civil war is, simply put, a war between citizens of the same country. Be it a division that falls along political, racial, gender, geographic region, or any other lines, if it is involves citizens of the same country who are at war with each other it is classified as a civil war. Civil Wars generally are fought for political independence (or dominance) of each side - they may or may not result in a splitting of the original country, but those wars where secession is a stated goal of one side (not just an outcome) are generally always considered a Civil War.

A revolution is a war fought to overthrow or rid yourself of a government in order to establish a new one. The old government may be indigenous, or may be external (i.e. colonial). In general, the main point of a revolution is to completely overthrow the existing government and replace it with a native government, NOT to split the country. Revolutions can be civil wars, but civil wars do not have to be revolutions.

For more clarity, here are examples:

The American Revolution was fought between citizens of the American Colonies, which, while nominally British subjects, did not consider themselves Englishmen. The "Americans" fought a revolution against their current government, which was British, as the purpose was to replace the entire government of the Colonies with a whole new government, independent of Great Britain.

The American Civil War is not a revolution, but a civil war. It was between two major political factions; in this case, one faction decided that it wanted to self-govern. It is classified as a civil war because (a) it was solely between citizens of one country (b) the point was political independence of one group, NOT the wholesale replacement of the national government for the entire country and (c) secession was a stated goal

The Chinese Civil War (1927-1950) is both a revolution and a civil war. It would be considered a civil war due to it being conflict between the Chinese themselves, specifically over the form of national government which would be used (republican or communist). It should be considered a revolution due to the fact that the goals of each side were dominance of the entire national government - that is, the struggle was over who should set the character of the national government, not for specific political rights or powers of individual groups. The fact that another war against an external aggressor (the Second Sino-Japanese War, which overlapped with World War 2) was also fought during that same time period does not change the nature of the overall revolutionary civil war being fought simultaneously.

Another distinguishing factor in modern times is that Civil War is often used to refer to any conflict with fighting on a large scale (even if it might be more properly termed a revolution), while a Revolution refers to a significant change of the type of government, and does not specifically have to include actual fighting (cf. the Velvet Revolution in Czechoslovakia).