Project management software; such as Microsoft Project, Trello, Basecamp, etc., are useful for organizing bigger projects. Software such as the ones stated have many more tools such as the gant chart which is horizontal calendar that shows when each project is to be completed, how much time is allotted for the task, and how much slack is given for the task.
The critical path is the sequence of tasks that have no flexibility in their scheduling and must be completed without delay or risk delaying the whole project.