I can't find any information on what exactly foam erasers are made of, but my guess would be a microporous reticulated foam (like melamine foam, for example).
Foam erasers are universally lauded as being excellent in cleaning graphite off of paper, leaving (virtually) no traces, without having to put anything near as much power into the rubbing as one would with classic rubber, plastic, or vinyl erasers.
This also means you are less likely to damage the paper you're working on.
They produce larger pieces of waste material - with the right technique you'll be able to produce a single piece of waste, which means cleaning up is far easier to do.
There is no maintenance involved.
There is one caveat, however: as you write about the 'performance', we have to take into account the amount of material used in relation to the erasion power, and here these erasers fall a little short: being foam, they are consumed a lot faster than standard erasers.