What is the difference between Salesforce Update and Salesforce Upsert connector?

Hi,

Update Statement
The update DML operation modifies one or more existing sObject records, such as individual accounts or contactsinvoice statements, in your organization’s data. update is analogous to the UPDATE statement in SQL.

Upsert Statement
The upsert DML operation creates new records and updates sObject records within a single statement, using a specified field to determine the presence of existing objects, or the ID field if no field is specified.