What is the difference with ETFs and index funds?

As quoted in our 'Money Clinic with Bestinvest' webinar:

They're very similar creatures, they're sort of collections of investments that map to an index, it's just ETFs you buy and sell like a share and index funds, you buy and sell like a fund. The purists will tell you that there's huge amounts of difference between them, we don't actually think there really is. You will get a transaction fee for buying and selling shares, typically. So if you've got smaller amounts, you might want to look to the fund. If you've got larger amounts, you might find it cheaper to access ETFs.