I just realize on coinmarketcap that some coins are called Asset (TIME, Tether, OmiseGo... ) while some are called Currency (Bitcoin, Ethereum, Ripple...). What is the difference and which type is better to hold?
Currency or Coins are like bitcoin a coin.
Asset or tokens are more like a share of a project. Most of this Asset tokens come from ICOs. Their main problem is that normally countries regulate such projects to secure asset owners so shareholders. all of it is sort of shady. Not only those that issued and sold asset and did it just to scam, but also those with good projects that will work hard to achieve them. I think all will need to answer some questions at the end.