What is a critical path in schedule network diagram?

When activity scheduling is done there will be activities whose start time and/or end times are not critical. It may be possible, due to dependencies, to start a task later than the date on the schedule, similarly an activity could be completed later as there are no other activity waiting for its completion. These time pads are called floats. There is always a path from start to finish, which does not have any floats. Not only all the activities in the path must be carried out in planned time, but also there cannot be any delays. Any delays will directly reflect on project completion time. This chain of activities or the path from start to finish is known as the critical path.