Define a demand-side platform (DSP).

A demand-side platform (DSP) is fundamentally designed to enable advertisers to purchase ad impressions from various sources in an efficient and automated manner. It provides the technology and infrastructure that allows advertisers to manage their advertising inventory and optimize their ad spending in real time. Within a DSP, advertisers can set their campaign parameters, target specific audiences, and utilize performance data to reach their marketing objectives effectively.

This system streamlines the process of buying advertising space across multiple supply sources, allowing for precise targeting and real-time bidding. It represents a critical component in programmatic advertising, where the goal is to maximize the effectiveness of ad spending through better targeting and automation.

In contrast, other options serve different functions: platforms for publishers are focused on selling inventory rather than purchasing it, user data analysis typically falls under different analytics tools rather than DSPs, and managing social media campaigns is outside the scope of what a DSP offers. Therefore, the definition that matches the role of a DSP as an automated purchasing system for ad impressions is clearly accurate.