Template appertains to a sample document that already has some details and information in place. It is a tool to enforce a layout with a look and feel across multiple pages or within the content area. Once the template is finished, the user/ designer can edit, manage or save the result as an ordinary document. But when you change any template, the pages or regions that are from that are from that template change too.
UI PSD Templates stands for User Interface Photoshop Document templates.
There are numbers of flat UI PSD templates available on the web for free. There are even new designs which are all free. In most UI PSD templates, login pages, icons for social media, audio and video ui player, buttons, profile page layouts and other layouts can be seen.
It is recommendable to download those high quality flat UI PSD templates as they are vector layered, so it not a problem if you scale to huge resolutions. The combination of colors of these flat psd ui templates is one thing to comment upon, and it will also look really good on your app / webpage.