This is a tricky question, since there are really three answers.
Broadly, yes, your story will be kept confidential. Managers and investigators all realize that allegations of harassment can be incredibly sensitive, and often involve details that any party would rather keep quiet. It is unhelpful for a workplace to become part of a rumor mill, and to have employees ostracizing each other, pointing fingers, starting whisper campaigns, or doing anything else to cloud the integrity of an impartial investigation. Managers should take great care to keep sensitive details as private as possible so as not to compromise an investigation or to impact the flow of the business.
However, a person accused of misconduct has the right to answer to those allegations, which will involve them learning the details of those allegations so that they can provide a full defence. They are instructed to keep all details private, however they will be informed of the nature and details of your complaint. Managers will also receive a full report from an investigator that outlines the nature of the story, but this too will be kept away from public view, and parties involved are only entitled to know the results of an investigation vs. receiving a full report.
The third answer that may arise is if there is any litigation. If a lawsuit stems from this incident, then the parties may be required to trade the report between their lawyers. If the report includes communication with a lawyer, or if it was made for the purposes of litigation then it may be a privileged document, however there is a possibility that the details will become part of a court proceeding.