ethereum is a open source network that use blockchain technology.
developers can use ethereum to build your personally cryptocurrency.
in this network thirs person can't access to my balance, it is safe place for hold our money. also price of the coins is unstable. so i can't buy ethereum and hold it for years withour risk. it is make me nervous and force me to be worry for my funds.
ETH blockchain is secure and safe for keep money in the midterm.
my advice is do enter on cryptocurrencies carefully even they offer good promotions.