Project site templates have been designed with tight team work in mind. If you are part of a team and require a site for planning out work, this site template will be ideal for you.
A task list is predefined by SharePoint which allows you to instantly set up tasks within your site. With this you can assign team members to tasks and have an email notification sent to them letting them know!
An OOB function of the Project site is the timeline, the timeline lets you put your tasks into a visual guide that helps project management. For those familiar with Microsoft Project, you will be familiar with a lot of the functionality including task dependencies and sub tasks.
If you prefer to keep to your local applications or work on the go with limited internet access you can Use Project with SharePoint. An advantage of this is project plan access to those working in industries not office based is being able to take your information anywhere.
Document collaboration is a great feature within SharePoint that allows team members to work together on documents, the Project Site allows you to do this out the box. Adding a lookup field to the task list, you can have documents assigned to tasks.
After your project site is set up and you have started using it, you may decide you want to share your project information with others, you may want to only show some information of the project to the client, the Project Summary Web Part will help you in achieving this.