Explanation
Manufacturing Cloud requires an account to create a sales agreement, which is a record that represents a long-term negotiated business relationship with a customer. An account is a standard Salesforce object that stores information about a company or a person that you do business with. You can also associate other objects with a sales agreement, such as contracts, quotes, orders, and forecasts, but these are not required to create a sales agreement. References: Salesforce Help: Create a Sales Agreement

Account manager targets are long-term goals that account managers set for themselves and their team members. They can be based on revenue, volume, margin, or any other metric that is relevant for the business.
The team member hierarchy type determines the users that account managers can assign targets to. It can be either the manager hierarchy or the forecasts hierarchy, which are defined in the Roles and Forecasts Hierarchy pages in Setup, respectively. If the team member hierarchy type is changed in account manager targets, all the existing targets are made read-only, as a warning message indicates. This is to prevent any inconsistency or confusion in the target assignments and approvals. To edit the existing targets, account managers have to clone them and make the necessary changes. References: Choose Team Member Hierarchy for Account Manager Targets, Set Up and Configure Account Manager Targets, Set Up Targets for Account Managers Unit | Salesforce Trailhead, Assign an Account Manager Target

A sales agreement is a record that captures the terms and conditions of a long-term or run-rate business relationship between a manufacturer and a customer. It can include products, product categories, prices, volumes, schedules, and other details. A sales agreement can have a maximum of 1500 products or product categories and 72 schedules. Contact Salesforce support if you want to increase the limits. Note that having a large number of product or product categories and schedules can affect system performance1. References: Considerations for Working with Manufacturing