Basecamp is unlike most project management programs that are based on Gantt, Pert or CPM style charting. These are very helpful in working out the order of the tasks in your plan, establish reasonable durations and find linkages and overlaps. Once you have this plan, it is easy to see how you are doing, but it is very cumbersome and time consuming to use it to manage the project. The problem is that this type of plan is like a wire frame perspective of a building; it is only meaningful to those who created it or spend a lot of time understanding it. On a day to day basis the chart is not a useful tool because it only communicates goals, not what is going on.
Basecamp, on the other hand, communicates what is going on - through its website and also through email direct to team members. Team members can then add or request clarifications. Basecamp facilitates collaboration and effortless communication, which after all is what project management is about. "Projects go well when people talk to each other, discuss issues openly, and communicate clearly. Basecamp is focused on making this easy."
Basecamp has several features that help with communication. Here are some of them.
... is a log of the latest activity in your project making it simple to see what has been happening.
"No more messy email threads. Post messages to Basecamp instead.
Instead of scattering emails all over the place, use Basecamp message boards to keep all the discussions about a project in one centralized location. You can even specify who can see which messages."
... can be added to messages by your team members. You can leave comments on to-dos and milestones too. This makes it easy for you to clear up any questions your client or team might have. And since they’re all stored in Basecamp, everyone knows where to go for the latest information.
See Basecamp's page about how TO-DOs work.
"Schedule project milestones.
Keep track of what’s due, when it’s due, and who’s responsible for getting it done. Milestones are great for scheduling project phases, due dates, and deliverables. See everything that’s coming up on your calendar. Works with Google Calendar, Outlook, Backpack, .Mac, and iCal."
... is a collection of all the relevant project files that you have uploaded to share.
... are like web-based Word documents. But unlike Word documents, many people can collaborate on a Writeboard at once. Writeboards keeps track of who wrote what. Plus, you can roll back to any previous version or compare versions side by side.
NOTE: Quotes in this post were taken from 37signals Basecamp website.
NOTE: This description applies to Basecamp Classic. The new Basecamp retains the same functionality, but some of the terminology has changed.
Other articles about Basecamp:
Basecamp / Nozbe Comparison
How To Hack 'Basecamp Personal'