Using a HDMI Cable
This is the simplest method, since you only need an HDMI cable. It will depend on the type of mobile device, some already bring the micro HDMI port, but in other cases it will be necessary to use an MHL microUSB to HDMI converter, such as the above image, which has cost about 8 euros.
All you have to connect the cable to your Android and the TV, and look for the HDMI source with the TV remote. Once done, you will have the screen of your smartphone or tablet on your TV and you can see games, apps, videos and your favorite content on the big screen.