Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images which represent scenes in motion. Video technology was first developed for television systems, but has been further developed in many formats to allow for consumer video recording. Video can also be viewed on through the Internet as video clips or streaming media clips on computer monitors.

Video resolution
 
Comparison of TV resolutionsThe size of a video image is measured in pixels for digital video or horizontal scan lines and vertical lines of resolution for analog video. In the digital domain (e.g. DVD) standard-definition television (SDTV) is specified as 720/704/640×480i60 for NTSC and 768/720×576i50 for PAL or SECAM resolution. However in the analog domain, standard definition equates to about 240x480 (NTSC) or 240x576 (PAL) pixels for VCR quality, to 400x480 (NTSC) or 400x576 (PAL) pixels for TV broadcasts (i.e. the number of horizontal scanlines [from top to bottom] remain constant, but the horizontal resolution [from left to right] varies). Aspect ratio is preserved because of non-square "pixels".
New high-definition televisions (HDTV) are capable of resolutions up to 1920×1080p60, i.e. 1920 pixels per scan line by 1080 scan lines, progressive, at 60 frames per second.

Video resolution for 3D-video is measured in voxels (volume picture element, representing a value in three dimensional space). For example 512×512×512 voxels resolution, now used for simple 3D-video, can be displayed even on some PDAs.

Video quality

Video quality can be measured with formal metrics like PSNR or with subjective video quality using expert observation.
The subjective video quality of a video processing system may be evaluated as follows:
Choose the video sequences (the SRC) to use for testing.
Choose the settings of the system to evaluate (the HRC).
Choose a test method for how to present video sequences to experts and to collect their ratings.
Invite a sufficient number of experts, preferably not fewer than 15.
Carry out testing.
Calculate the average marks for each HRC based on the experts' ratings.

from : en.wikipedia.org