you can use theme with responsitive as: themejunkie, theme forest, themify..

go for Wordpress FrameWork it woks nice and responsive

Responsive web design (RWD) is an approach to web design aimed at crafting sites to provide an optimal viewing and interaction experience—easy reading and navigation with a minimum of resizing, panning, and scrolling—across a wide range of devices

for responsive website,use plugin if it was created in php or other but if it was created in java and .net it is already responsive.

tons of theme for WP are responsive.
Wix site are all responsive.

Responsive Web design is the approach that suggests that design and development should respond to the user's behavior and environment based on screen size, platform and orientation. The practice consists of a mix of flexible grids and layouts, images and an intelligent use of CSS media queries.

Responsive Website
 

I am working with online store, BatteryBhai.com. This is Responsive site and run all the online platforms.

The Site which adapt automatically for the Size of the display is called as Responsive design website...

we will figure out how to make our own responsive WordPress subject utilizing Bootstrap. Bootstrap is a responsive system for building sites and applications, and it's an incredible beginning stage for building a responsive WordPress theme.you don't need to have constructed a topic starting with no outside help before to effectively take after along.

Search on google to get more and more responsive theme.

The Website Which adjust size automatically with respect to the Screen is called responsive website..

Responsive web design is an approach to web design aimed at crafting sites to provide an optimal viewing experience—easy reading and navigation with a minimum of resizing, panning, and scrolling—across a wide range of devices

You can try bootstrap templates. It's responsive.

You can use Thrivetheme, It's all responsive

You can use Thrivetheme, It's all responsive