What is an ERC20 token?
ERC20 is an Ethereum Standard and was published at the end of 2015. It defines certain standardized methods for Smart-Contracts. For standard tokens, it allows third parties to process information and perform transactions without knowing the specific token. New projects can issue tokens using the standard template without developing their own blockchain or until their own blockchain is developed.
Examples for ERC20 tokens:
OmiseGO, Golem, EOS, TRON
On which wallet can ERC20 tokens be managed?
The best known wallet is MyEtherWallet.
To prevent access by third parties and to increase security, it is recommended to use it in combination with a hardware wallet (Trezor, Ledger Nano S).