what is the best video format for iMovie?

I'm a basic newbe on imac compiuters. Although I like it the transition is a bit painful.

I download stuff from my (cheep) video cameras BUT after closing the oniginal window I can't find the vids OR pictures I just downloaded from the devices.

I am hsving a difficult time figuring out what is the BEST video promat to record in that can be used in imovie AND final cut pro.

I'd appreciate any assoistance at this point.

All tips appreciated,

:-) Cheers