Some reading that may help...
Codec & Format information, with 2 links inside to read -read both links in reply #1 http://forums.adobe.com/thread/1270588
Report back with the codec details of your file, use the programs below... A screen shot works well to SHOW people what you are doing
http://forums.adobe.com/thread/592070?tstart=30 for screen shot instructions
Your question is too non specific for us to help you. You are going to have to give more background information to place your question in context with something.
What version of Premiere Elements are you using and on what computer operating system is it running?
Generalizing....when you have interlaced video, each frame is made up of fields. These fields can present with either upper field first or lower field first. A good understanding of interlaced (fields) vs progressive video can be obtained from the following link
If you are trying to decide how to use your video source in Premiere Elements, please detail the properties of the video source...video and audio compression, frame size, frame rate, interlaced or progressive, file extension, pixel aspect ratio. How do you want to export your Premiere Elements Timeline containing your edited source video?
Let us start here and then decide what next.