Difference between Assigning a Goal to Someone and Cascading it from the New Goal

Cascading a goal:
This is usually used for Achieving/Tracking Team/Project Goals where the collective contribution is required from different team/project members (including yourself if necessary). Cascaded Goals are easier to Track as they give you a one place view of the overall status of Master Goals as well as the Contributing goals (sub-goals). Please refer to the example with the screenshots below. Cascading promotes the concepts of Goal Alignment which translate into a hierarchy view of the goals linked/aligned to each other across the organization thereby contributing to the achievement of the Overall Company goal.
Assigning a goal:
This is usually used when the goal is specific to a particular employee and is he/she is the sole contributor to that goal. Even though they contribute to the organization indirectly, they are not necessarily to be aligned with one of the department company goals. Please refer to the example with the screenshots below.

Specific Examples:

Cascaded goal 
For example, you have a goal which is increasing the client retention objective. Various departments are also involved in retaining the client( eg the sales department, Customer Success department, etc). So this a cascaded goal where all these departments have the same goal which is retention of a client.
 Assigned Goal: 
For example, a sales manager can assign a target to his/her direct reports like achieve 40 clients by the end of this year. Also, the sales manager can also have an individual target that is for themselves which needs to be achieved at the end of the year.