"Start and wait approval" and "Create an approval"
Start and wait, will pause the workflow until the approval is given.
Create approval will create an approval and not wait. Essentially you would want a seperate wait for approval action, otherwise there is not really much point in having the approval at all as you cannot do anything with it once its completed.
For your scenario use start adn wait for approval, you can link to the item for the approver to update in the approval action.