Index funds are divided into:

1. Closed-end index fund: it can be traded in the secondary market, but it cannot be purchased and redeemed.

2. Open-ended index funds: they cannot be traded in the secondary market, but they can be purchased and redeemed from fund companies.

3. Index ETF: It can be traded in the secondary market or purchased and redeemed, but the purchase and redemption must be in the form of portfolio securities.

4. Index LOF: It can be traded in the secondary market or purchased and redeemed.