Civil society is the "aggregate of non-governmental organizations and institutions that manifest interests and will of citizens." Civil society includes the family and the private sphere, referred to as the "third sector" of society, distinct from government and business. Dictionary.com's 21st Century Lexicon defines civil society as 1) the aggregate of non-governmental organizations and institutions that manifest interests and will of citizens or 2) individuals and organizations in a society which are independent of the government.
Sometimes the term civil society is used in the more general sense of "the elements such as freedom of speech, an independent judiciary, etc, that make up a democratic society" (Collins English Dictionary). Especially in the discussions among thinkers of Eastern and Central Europe, civil society is seen also as a concept of civic values. One widely known representative of this concept is the Polish former dissident Adam Michnik.
Volunteering is often considered a defining characteristic of the organizations that constitute civil society, which in turn are often called "NGOs", "NPOs", or CSOs. Most authorities have in mind the realm of public participation in voluntary associations, trade unions and the like, but it is not necessary to belong to all of these to be a part of civil society.