At the meeting, the reporter presented this year's sales figures.
The presenter explained the survey results in detail.
発表者 emphasizes the act of presenting or announcing, often at conferences or events, whereas 報告者 focuses on the reporting aspect, which may include detailed accounts or formal reports.
Compound of 報告 (ほうこく, 'report') + 者 (しゃ, 'person'). The word follows a common pattern for forming agent nouns in Japanese.