What is commonly used to represent a timeline that outlines tasks against time?

A Gantt chart is specifically designed to represent a timeline for project management and outlines tasks against time effectively. It visually showcases the duration of each task, helping teams understand start and end dates, overlaps, and dependencies among tasks. This type of chart provides clarity on the sequence of tasks and allows project managers to monitor progress easily, making it an essential tool in planning and scheduling.

In contrast, the other options serve different purposes. A bar graph is primarily used to compare quantities of different categories, while a histogram displays the distribution of numerical data. A line graph is used to show trends over time, but it is not inherently structured for task scheduling as a Gantt chart is. This focus on timeline representation makes the Gantt chart the most appropriate choice for outlining tasks against time.