Buttons and links only display for users who have the appropriate permissions to use them.
For example, users who do not have the “Delete” permission on opportunities do not see the Delete button on an opportunity detail page. They also don’t see the Del link on an opportunity related list.
Salesforce Classic
he Sharing button lets users grant other users access to a record beyond the organization-wide defaults or sharing rules. You can easily remove this access after it’s no longer needed.
You have access to the Sharing button when your sharing model is either Private or Public Read Only for a type of record or related record. For example, the Sharing button may appear on an account even though your organization-wide default for accounts is Public Read/Write, if your organization-wide default for related opportunities is Public Read Only.
When the button is available on the page layout, administrators see the button on all records. Non-administrators see this button on records that only they own.