A global tracker buys a world share index, so one fund can hold anything from about 1,250 to 4,200 companies. At 30 September 2026 the United States made up 62.28% to 72.94% of the three main world indices, so a global fund is mostly a US and dollar fund.
An index fund buys the holdings in a market index so its return follows that index, minus costs. Before buying, compare the total cost, how closely it has tracked, how it copies the index, the unit class and the tax wrapper.
Open-ended funds and ETFs can track the same index at similar cost. The difference is how you buy them: funds deal with the manager at a forward price, ETFs trade on an exchange all day with a spread, and their tax and stamp duty rules differ.
An ETF is a fund whose shares trade on a stock exchange like a company's, usually tracking an index. You buy it through a share-dealing account, ISA or SIPP at a live price, paying the ongoing charge plus dealing costs and a spread.