In Project, a relationship between two tasks is known as a task dependency or task link. Defining the dependencies between tasks helps you determine which tasks start when, as well as when the project might finish (Biafore, 2010, p. 70).In any Project there will be an order in which tasks need to be completed - a wall can't be built until it has a foundation, on premise software can't be configured until it is installed.
There are two types of tasks in dependency relationships: the predecessor and the successor. Successor tasks are dependent on predecessor tasks. (Daley, 2011, p. 46)
This is the most common dependency type, and is the default type set when you link tasks in Microsoft Project. A Finish-to-Start dependency means a task can't start until its predecessors have finished. In other words Task B can't start until Task A has finished.
A task can't start until its predecessors have started. For example, Task B can't start until Task A has started.
A task can't finish until its predecessors have finished. For example Task B can't finish until Task A has finished.
A task can't finish until its predecessor tasks have started. For example Task B can't finish until Task has started.