There is much confusion about what it means to have a separation from your spouse.

An informal separation simply means that you and your spouse are living apart. There is no legal document or court involved.

A legal separation can take two forms: the separation can be according to a binding, written Separation Agreement between you and your spouse, or the separation is in compliance with a judge’s determination that you are legally separated. The latter, called a judicial separation, is very rare.
Almost all legal separations are formalized in a binding written Separation Agreement. Except for dissolving the marriage, all issues are resolved, including custody, visitation, spousal support, child support, division of assets, medical insurance, life insurance, and all other financial issues between you and your spouse. There are also provisions in the Separation Agreement that state that you and your spouse have the legal right to live separate and apart from each other, and not to be disturbed by the other spouse, as if you were single and unmarried. However, you are not yet divorced, so you cannot marry another person. (If you do so, you are committing bigamy, which is a crime in the State of New York.)