Explanation
My Domain is a feature that allows administrators to create a custom domain name for their Salesforce org that replaces their instance URL (such as na35.salesforce.com). My Domain provides benefits such as improved security; enhanced branding; faster navigation; access to Lightning components; etc. However, one of the considerations when enabling My Domain is that it changes how users log in to Salesforce - instead of using their instance URL login (such as login.salesforce.com), they have to use their My Domain login (such as mydomain.my.salesforce.com). This applies to all internal and external users who access Salesforce via web browser or mobile app. References:
https://help.salesforce.com/s/articleView?id=sf.domain_name_overview.htm&type=5

Explanation
Role hierarchy and sharing rules are two features that should be used to open up access to Opportunity records for sales users working on collaborative deals. Role hierarchy can be used to grant access to records owned by or shared with users who are below them in the hierarchy. Sharing rules can be used to extend sharing access to users in public groups, roles, or territories based on certain criteria, such as record owner or field value.
References: https://help.salesforce.com/s/articleView?id=sf.admin_sharing.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.security_sharing_rules.htm&type=5

Explanation
A junction object is a type of custom object that allows administrators to create many-to-many relationships between two other objects. A many-to-many relationship means that each record of one object can be related to multiple records of another object, and vice versa. For example, a junction object can represent that a contact can be interested in multiple pieces of merchandise, and a piece of merchandise can be of interest to multiple contacts. A junction object has two master-detail relationships with the two objects it connects.
References: https://help.salesforce.com/s/articleView?id=sf.relationships_manytomany.htm&type=5

Explanation
Two functions that an administrator should use when creating a validation rule are:
Error condition formula, which defines when an error should occur based on record fields and values Error message location, which specifies where on the page layout an error message should appear when triggered by an error condition formula Formula return type and rule active date are not functions used for validation rules. References:
https://help.salesforce.com/s/articleView?id=sf.validation_rules_overview.htm&type=5

Explanation
When you mark a field as required in Object Manager, the field is universally required to save a record on that object in the user interface. However, the field is not required to save records via the API on that object, unless you also mark it as required on the page layout.
References: https://help.salesforce.com/s/articleView?id=sf.fields_about_required_fields.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.admin_profile_picklists.htm&type=5