Can someone help me about what this skin name is

[samisyed416]

[samisyed416]

[thinktink]

Looks like Bento/Big Bento

[Aminifu]

Looking at the size of the headings in the title bar and the spacing between them, I would say this is a screenshot of the Big Bento skin.

You can look in the Options - Preferences - Skins tab. It lists all the installed skins in your configuration and the active skin is highlighted.