What is the difference between formatting your SD Card and erasing/deleting files inside it?

Answer 1

Formatting your cards is the best and safest way (for your card) to erase data from your cards (provided it's done on the camera itself).

Compare it to getting a haircut vs individually plucking hairs from your head. Deleting individual files agitates your card and wears it out allot faster than formatting the card will. But don't format too often as that's not good for the card either.

Remember it's better to delete from the computer and format from the camera. Doing it that way causes less damage.

Answer 2

if you store files on any kind of hard disk or card or such there's two things stored... the actual data and the location of that data in the register (file allocation table/FAT or whatever other format is used...) if you delete a file the actual data remains, but the entry in the FAT is erased. next time you store data it will (probably) write over the old data... if you format a disc you erase the entire FAT but the actual data still remains... if you want to really really really erase the data you'll want to format the disc and then write over all the data that is still there... there's special software that does that for you