The difference between fixed units and fixed duration can be seen when modifying the units and work for a task. For Fixed units tasks, when revising units and work -duration is recalculated. For fixed duration tasks, when revising units - work is recalculated and when revising work-units are recalculated.

To change a task type, double click on the task name in the Gantt Chart, then in the Task Information dialog, go to Advanced tab and in the Task Type group select Fixed Units, Fixed Work or Fixed Duration and then click OK.

If you edit the duration of a fixed work task, nothing happens. Changing scalar work after making an assignment on a task will no longer automatically alter the Assignment Units field.

To see the Task Mode field, use Insert column option under Format menu and select in the Field Name: Task Mode.

You can insert and display this column in views like Gant Chart, Tracking Gant or Task Sheet view. 

Task Mode column displays an icon indicating whether a task, is a manually scheduled task, or an automatically scheduled task.

Lead time is overlap between tasks that have a dependency.

For example, if a task can start when its predecessor is half finished, you can specify a finish-to-start dependency with a lead time for the successor task. You enter lead time as a negative value.

Lag time is a delay between tasks that have a dependency. 

For example, if you need a two-day delay between the finish of one task and the start of another, you can establish a finish-to-start dependency and specify two days of lag time. You enter lag time as a positive value.

To make a manual task a milestone, double-click on the task. In the Task information - Advanced tab, check "Mark task as milestone" - click OK.

A task note is a written message associated with a task.

To insert a recurring task in your project, on the View menu click Gantt Chart – select the row below where you want a new recurring task to appear – click on Insert - Recurring task option under Task menu.

To split a task, go to menu Task-Split then drag and drop from a Gantt Bar in order to create a split in the middle of the bar.