Sell-side equity research typically refers to the equity research groups of investment banks. These groups are responsible for analyzing a specific sector in the stock market, and will typically cover 8-20 stocks within any given sector. They write equity research reports which provide an opinion to public investors as to what the fair price of a stock should be, and these reports are typically backed by projection models and sometimes DCF analysis.
Given the importance of financial modeling in such a role, equity research analysts and associates require strong financial modeling and technical skills.