In the United States, Esquire is mostly used to denote a lawyer

In the United Kingdom, Esquire historically was a title of respect accorded to men of higher social rank, particularly members of the landed gentry above the rank of gentleman and below the rank of knight. It later came to be used as a general courtesy title for any man in a formal setting, usually as a suffix to his name, as in "John Smith, Esq.", with no precise significance. In the United Kingdom today, it is still commonly used as a written style of address in formal or professional correspondence.[4][5] In certain formal contexts, it remains an indication of a social status that is recognised in the formal Order of Precedence.[6]

In the United States, Esquire is mostly used to denote a lawyer, in a departure from traditional use, and is irrespective of gender. In letters, a lawyer is customarily addressed by adding the suffix Esquire (abbreviated Esq.), preceded by a comma, after the lawyer's full name.[7]