To take a 10 second video with your Raspberry Pi camera type the following into LX Terminal
raspivid -o video.h264 -t 10000
raspivid = is the utility that is part of Raspbian (the Raspberry Pi operating system) which is used to capture video.
-o = sets the output filename for the video
video.h264 = is the file name (h.264 is a new video codec standard which can achieve high quality video in relatively low bitrates. You can think it as the “successor” of the existing formats (MPEG2, MPEG-4, DivX, XvidD etc.) as it aims in offering similar video quality in half the size of the formats mentioned before.
-t = sets the time the program will run in milliseconds.
10000 = 10 seconds