These are cooked rotten eggs, the eggs have a strong sulfurous smell and rich flavour. If you get use to the smell then you can eat these for their flavour (and texture, then tend to be spongy due to gas bubbles that get trapped when cooked).
Usually sold already cooked (steamed) to halt the rotting process at the right stage.
My Filipino friends say this is eaten as an afrodisiac for men in the Philippines.
Look for stalls selling eggs on sticks, there will usually be a selection of eggs, barbecued eggs, rotten eggs, and foetus eggs. You can tell the rotten eggs by smell.
Rating: Give them a miss unless you like old fish sauce.