Sample中 ， Tab 在上， Navigation 在下， 后者有图标。不理解为什么用不同的名称。之前没有区分，混淆模糊。
搜索发现有人在 stackoverflow 问。有人答曰：区别在于 Tab 是同一主题， 而 Navigation 可用于不相关的主题。
Tabs are considered to be related to each other where as Navigation Bar are not.
Tabs are generally used to segregate data are somehow related. Like A profile can be displayed in Tabs where it can be divided in Personal, Professional, Education tabs. It is mainly used to show data about the same hierarchy but different in nature and also for organizing the data.
On the other hand, Navigation Bar as it suggests is used for different topics which might not be inter related.
For a User, which doing User Testing, we saw that Users think that when clicking on a Navigation Bar they will be taken to a separate page which might not/ or may be related to the current page. They take it to be like normal Navigation links which can be like About us page and Contact Us page. Same user for Tabs, thinks that he will be in the same page but will see related data to the parent or the opened tab. He doesn't expects that the page will navigate to a completely new page with no related data.
https://ux.stackexchange.com/questions/23527/what-is-the-difference-between-a-navigation-bar-and-tabs