Starting on the left side of the photo example provided here are 5.1/7.1 Channel analog outputs, which are included mostly on higher-end players. These connections provide access to internal Dolby (TrueHD, Digital) and DTS (HD Master Audio, Core) surround sound decoders and multi-channel uncompressed PCM audio output of the Blu-ray disc player shown here. This is useful when you have a home theater receiver that does not have digital optical/coaxial or HDMI audio input access, but can accommodate either 5.1 or 7.1 channel analog audio input signals.
In addition, just to the right of the 5.1/7.1 channel analog audio outputs are a set of dedicated 2 channel stereo audio outputs. This is provided not only for those that do not have surround sound capable home theater receivers, but for those that prefer a 2-channel audio output option when playing standard music CDs. Some players provide dedicated Digital-to-Analog converters for this output option. However, it must be noted that in some cases the two-channel analog outputs may be combined with the 5.1/7.1 channel analog outputs - in other words, you would use the front left/right outputs of the 5.1/7.1 channel connections for two-channel analog audio playback.
Moving to the right of the analog audio output connections are both a Digital Coaxial and Digital Optical audio connections. Some Blu-ray Disc players have both of these connections, and others may only offer one of them. Either connection can be used, depending on your receiver. However, if your receiver has 5.1/7.1 channel analog inputs or HDMI audio access, that is preferred.
Next are two analog video output options. The yellow connection is the Composite, or standard analog video output. The other output option shown is Component Video output. This output consists of Red, Green, and Blue connectors. These connectors plug into the same type of connectors on a TV, Video Projector, or AV receiver.
You should not use the composite video output if you have an HDTV as it will only output video in standard 480i resolution. Also, while component video connections may output up to 1080i resolution for Blu-ray disc playback (see exceptions), they can only output up to 480p for DVDs. The HDMI output connection is required for viewing Blu-ray in 1080p and standard DVDs in upscaled 720p/1080i or 1080p.
Next is the Ethernet (LAN) port. This allows connection to a high-speed internet router for access Profile 2.0 (BD-Live) content associated with some Blu-ray Discs, internet streaming content from services, such as Netflix, as well as allowing direct download of firmware updates.
Moving further right is a USB port, which allows the connection of a USB flash drive, and, in some cases allows for connection of an external hard drive, iPod with audio, photo, or video files, or external USB WiFi adapter - refer to your own Blu-ray Disc player's user manual for details.
Next is the HDMI connection. Of all the connections shown up to this point, the HDMI connection is one that included on all Blu-ray Disc players.
HDMI allows you to access the 720p, 1080i, 1080p upscaled images from standard commercial DVDs. In addition, the HDMI connection passes both Audio and Video (both 2D and 3D depending on the player). This means on TVs with HDMI connections, you only need one cable to pass both audio and video to the television, or through an HDMI receiver with both HDMI video and audio accessibility. If your TV has a DVI-HDCP input instead of HDMI, you can use an HDMI to DVI Adapter cable to connect the Blu-ray Disc player to the DVI-equipped HDTV, however, DVI only passes video, a second connectcion for audio is needed.
A final note is that some 3D Blu-ray Disc players may have two HDMI outputs. For more on this, read my article: Connecting a 3D Blu-ray Disc Player with Two HDMI Outs to a Non-3D Home Theater Receiver.
Proceed to the next photo...