Several video files include some audio tracks (probably the translation for different languages). In this case, it is necessary to mention, what audio track to choose for the conversion.
Besides, DVD, as a rule, can contain some episodes. While opening DVD, the program, automatically, chooses the longest episode and makes it active. In the majority of cases, it appears to be the main fragment of the video, but sometimes you will have to choose the episode by yourself. Moreover, DVD-film can be divided into two or more episodes, so you can face the necessity to split them together. In this case, you need to open DVD some times and then, sequentially, point the needed episode at each opened file. After the conversion, only the episodes, you have chosen, will be present in the result file.