Flat design is a user interface design style that uses simple, two-dimensional elements and bright colors. Flat design was originally developed for responsive design, where a website’s content scales smoothly depending on the device’s screen size. With the use of simple shapes and minimal textures, flat design ensures that responsive designs work well and load fast.
Realism or Skeuomorphism is a term most often used in graphical user interface design to describe interface objects that mimic their real-world counterparts in how they appear and/or how the user can interact with them. A well-known example is the recycle bin icon used for discarding files. Skeuomorphism makes interface objects familiar to users by using concepts they recognize.
I attached a couple photos of flat designs vs. realism.
Tell me which style you like best!!