What the law treats as harassment
Harassment in the legal sense is unwelcome conduct connected to a characteristic the law protects, which covers far more than sexual conduct and includes harassment based on race, religion, disability, and other categories. It can come from a supervisor or a coworker, and New York law also reaches harassment of and by people who are not employees, such as clients and vendors, where the employer knew or should have known about it. Mistreatment that has nothing to do with a protected characteristic is usually not covered by discrimination laws, although it can raise other questions. New York requires employers to maintain a written harassment prevention policy with a complaint form and to provide regular training, so the policy is a good place to start reading.
When a complaint is made
Using the channel the policy describes, and putting the complaint in writing, tends to make the timeline clearer later. Keep a copy of what you sent and any response. Most employers then open an investigation that involves interviews with you, the person accused, and witnesses, and you may be asked to keep the process confidential, although complete confidentiality is rarely something an employer can promise. Temporary changes, such as separating schedules or reporting lines, are common while an investigation runs. Retaliation for reporting in good faith is unlawful in its own right, so keep the messages and reviews that show any change in how you are treated, and ask a lawyer how to record the rest.
When you are the employer
A complaint triggers obligations quickly. Who investigates, how interviews are documented, and what interim steps are taken all tend to be examined later if the matter becomes a claim. When counsel conducts the investigation, whether the work stays privileged depends on how the role is set up from the start. Discipline decisions should follow from findings rather than precede them, and the person who complained should not see a change in duties that looks like a consequence. We talk through the facts reported so far, the policy in place, and the order in which the next steps should happen.