Question: What is a Project Task?
In simple terms "It provides a Gantt chart which enables the scheduling of project work activities".
I think we are now good to go and implement this wonderful concept.
Step 1: Open SharePoint 2010 Central Administration and navigate to a specific site:

Step 2: Select project tasks from the listed category. Give a name to the project tasks:

Step 3: The project tasks are now created. The site looks like this:

Step 4: Adding new tasks:

Step 5: Adding new tasks - dialogue box:

Step 6: The project tasks are now created; the site now looks like this:

I hope this article is useful for you.