Gantt charts are a way of keeping track of projects you're doing so that you can manage them more effectively. More than just a list of tasks to work on, Gantt charts provide a visual component to help you see which jobs must be done consecutively or concurrently to help you stay on top of your workload.
Bright Hub has a series of useful articles on using Gantt charts:
There are computer-based tools for creating Gantt charts, such as Microsoft Project for Windows and OmniPlan for Macintosh, but they tend to be expensive. Web-based tools tend to require paid subscriptions, though some offer an option for a limited free account.
If you need to collaborate with others on your project, you may turn to BaseCamp, an online project-management tool created by the firm 37 Signals. It's used by businesses and other groups to coordinate work efforts. Typically there's a fee associated with using the application, but BaseCamp Classicis a free version with no time limit. William Fenton at PC Magazine wrote a review.