ETN is an acronym that stands for Exchange Traded Notes or notes traded on the Stock Exchange. These notes are securities with no maturity date or a product similar to zero-coupon bonds with very long maturities, the returns on which are linked to an index.
ETNs are close relatives of ETFs and these are collected in the macrofamily of FTEs. The difference between ETNs and ETFs is that the former are the notes and the second funds. This means that while ETFs track indices of the stock market or bonds or sectoral level, the ETN also replicate these ratios. However, they are not connected to a title in the sense of its direct ownership, but only to the issuer. For this reason when the issuer of an ETN fails, the investor has not received a loan guarantee in contrast to what happens with ETFs. Technically it is said that they are subject to counterparty risk. To avoid this problem they often provide issuers to collateralize the ETNs, to set aside or to another account a sum of money or a quantity of raw materials that serve as collateral for the investment in the ETNs.
ETCs are a subset of the ETN and share all the characteristics cited above but are identified by the nature of the underlying that for the ETC can only be a raw material while for the ETN may be all other cases.