Closed-end mutual funds are a lot like standard mutual funds, except that they are generally affected less during major market swings than a standard mutual fund, and they are traded on the open market, much like a regular stock.
Much like a regular mutual fund, closed-end mutual funds are managed by professional account managers. However, closed-end mutual funds cannot be purchased by simply mailing out a check like you could for a regular mutual fund using a calculated Net Asset Value determination. This of course is because they are traded on the open market, so you would purchase them in a similar manner.
Generally the best thing about a closed-end mutual fund is that you are given a discount over the market value. This essentially means that the value of all of the stocks in the portfolio are generally worth more than the actual market value suggests. This means that you are buying portions of a company for far less than what you normally would expect to pay. As the stocks rise in value, this discount becomes smaller, until the market value is more than what it should be for the stocks in the portfolio. Once this happens, you have a premium fund. This basically means that you are paying more for the fund than you really should be. However, if you see this portfolio as being a high riser, this could still be in your eyes a discount, if it looks as if it will keep rising.
Generally the best time to purchase a closed end fund is right after they are first released. They generally sell at a discount in the beginning, so you will be able to purchase them with a better chance of making money.
As a whole, closed-end funds are relatively safe to buy into as most managers select only high end stocks that are making predictable market moves. This allows the portfolio to be stable while still having an opportunity for substantial growth.