A civil union is a legal relationship recognized by some jurisdictions that give couples, usually of the same sex, the legal and economic rights of marriage. Civil unions are often established to give couples legal protections and privileges that married couples enjoy without using the term "marriage". These rights and benefits may include inheritance rights, medical decision-making authority, tax benefits, and more.
Civil unions were initially introduced as a way to provide legal recognition and protection to same-sex couples in places where same-sex marriage was not yet legally recognized. Over time, as many countries and states have moved toward legalizing same-sex marriage, civil unions have become less common and relevant in these areas.
It is important to note that the legal rights and implications of civil unions may vary depending on the jurisdiction in which they are established. Some jurisdictions may grant civil union partners nearly the same rights as married couples, while others may have more limited legal protections associated with civil unions. As of September 2021, the last update to my knowledge, the legal landscape around civil unions and same-sex relationships may continue to evolve in some regions.