An ETF is an Exchange Traded Fund which is in fact a share which is listed on the JSE. Just like Sasol, SAB or Pick ‘n Pay are shares which are bought and sold on the stock exchange, so is a Satrix ETF.
The ETF holds all the shares represented in an index and offers diversified exposure to a particular area of the market E.g. the Satrix TOP 40 ETF holds 40 of the largest stocks traded on the JSE by market capitalisation.
Investors buy shares in the ETF, which represent a proportional interest in the pooled assets within the fund.
It's the same as a Unit Trust in every aspect, except one, which is hinted at in the 'exchange-traded' part of its name.
As an exchange-traded fund, investors buy shares in the fund on a stock exchange and in the same manner as you buy shares in a stock, you can buy or sell an ETF whenever you want as long as the market is open.