This summary is not the rule. The rule text controls.
Tennessee used to have separate types of lawsuits, with different rules depending on whether you were suing in "law" or in "equity." This rule gets rid of that old split. Now, no matter what kind of legal problem you have or what kind of relief you want, you file the same type of case: a "civil action."
This matters because it makes things simpler for anyone going to court. You don't have to figure out which old category your case fits into or follow different sets of procedures based on that label. One set of rules applies to civil cases, which cuts down on confusion and technical mistakes that used to trip people up before their case even got started.