Will the reported user know that I had reported them?

Reports are anonymous, in relation to other users, and the people who receive reports cannot see/know anything about the reports against their posts or profile.

However, please keep in mind that if your report is against a private message and the user gets a Warning about something that happened in that private message, it can be obvious that the user of that private message has reported them.

Only the SW Staff can see all the details about a report.