Tasks lets you manage your to-do list while you’re on the go. You can create lists of things you need to get done and check off tasks as they’re completed. Just go to http://gmail.com/tasks in your phone’s web browser to access Tasks.
If youâ€™ve already installed Tasks on Gmail, they will show up automatically. As you add or cross out tasks, they are automatically synced with your task list on Gmail. In addition to a stand-alone to-do list, you can also now convert e-mails into tasks. Unfortunately, you cannot yet share task lists with others or make lists if your mobile phone is not connected to the Internet.
More info: Google Tasks list