AviDemux is designed to work with video files. If the video and audio codecs are the same, and the resolution, frame rate and other parameters of the videos are the same, you can join them together.
To do this you import the first video, then click on File-->Append to add the second one. You can join several videos this way.
AviDemux can also be used to add subtitles or audio streams to an existing video, if that is what you are asking.