It can be easily understood the difference between altcoin and token: the platform.
Coin is a Cryptocurrency which operates independently of any other platform. For eg. Bitcoin, Dash and Litecoin.
Token is a cryptocurrency which requires another platform, such as Ethereum, to exist and operate. For eg. OmiseGo, Golem, TenX, Tether & Gas.
Yes, I agree. Coins are standalone cryptocurrencies that do not require another platform to run, whereas Tokens are actually built on other platforms and they exist on that platform.