Keep in mind that the specific layout of connections may vary from brand to brand and model to model, and you may also have additional connections or duplicate connections not pictured here.
On this projector example, starting from the far left is the AC power connector where the supplied AC power cord plugs in.
Moving right there are several connectors. Starting near the top is an HDMI input. The HDMI input allows digital transfer of video from a DVD player or other source component with either an HDMI output or a DVI-HDCP output via a connection adapter.
Just to the right of the HDMI input is a VGA-PC Monitor input. This input allows you to connect a PC or Laptop and use the projector to display your images.
Just below the HDMI input is a Serial Port for external control, and other possible functions, and a USB port. Not all projectors will have these inputs.
Moving further right, on the bottom center of the rear panel, is a 12V trigger connection that allows certain types of wired remote functions.
Moving to the right side of the rear panel of the video projector, and beginning towards the top, we find the Component video inputs. The Component video input consists of Green, Blue, and Red connectors.
Just below the Green Component video connection is the S-Video input. Lastly, just below, and slighty to the right, of the S-video connector is the yellow connection which is the Composite, or standard analog video input. Your source components, such as a DVD player or AV Receiver will have one or more of these type connections. Match the correct connection of your source component to the same type of connection on the video projector.
One thing you will notice is the absence of any type of audio connection. With very few exceptions, video projectors do not have provisions for audio. Even though HDMI has the ability to pass audio as well as video, this function is not used on video projectors. It is the intention for the consumer to use an external home theater system, stereo system, or amplifier to provide the audio functions.
For more information on Video Projectors, check out my reference article: Before You Buy a Video Projector and my Top Picks for Video Projectors.