Newbie alert.
PAL DV is 720x576 = 1.25:1 aspect ratio.
Standard TVs are 4:3 = 1.333:1 aspect ratio.

This I understand.
Importing PAL DV into video editor = 1.25:1 aspect ratio if we're talking width versus height on a pixel basis.

This means it's not in the correct aspect unless settings are made to output in 4:3, which vary with the software package.

All this I understand.

The questions
1) Why do TVs have rectangle pixels to start with?
2) Do video cameras record in square pixels? Do their sensors have square pixels, or rectangle?
3) I have a PAL miniDV camcorder that displays in proper 4:3 aspect ratio on its LCD. Is this because the LCD has rectangular pixels or the sensor has or both?