These are image-based tabs.

These tabs have additional settings, so selected tab looks like it was brought to the front.
This effect is achieved with the help of additional items with individual styles. So, the structure of tabs looks like this:

Item1 separator Item2 separator Item3 separator Item4

Where separator is the additional item, that creates bring-to-front effect.
Each separator has 7 states:

                                   

For more details see parameters info.

These are Glass Style tabs.

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These are image-based tabs.