Can I use
tty to call Media Player and watch a video? Or run a browser in it? Since
tty is just a virtual terminal.
Regarding the question in the title: Between your OS and the DE there is another layer, typically X11 (what happened to Wayland?). The OS offers the framebuffer, a device file more or less representing the active video RAM. The X11 layer offers virtual display areas to applications (typically "windows") and composes the complete screen out of that (probably using the GPU of the system). Upon this you can use a desktop environment, doing all that window handling, decorations, global menus and stuff.
Most graphical application require X11 to run, but if you just want to watch videos, there are solutions with just the framebuffer, see here for example.
To run a graphical web browser on the framebuffer, see some projects and workarounds in these answers. It's old, so find out which projects are still active.
You can use TTY for that ONLY for special programs built for that.
- programs that work directly on frame-buffer (fbdev)
- programs that use ASCII display only even for semi-graphical
- programs that use standard old VGA/VESA hardware mode directly drawing their own display from 0x13 interruption...
for example lynx browser can be used (no images, no video, no CSS, no Flash and so on...) but works perfectly for all the rest. mplayer can use framebuffer to run videos, for example... but 99% you won't ever find quite modern programs work without XWindows.