Industry-specific funds attempt to capture the movements of a single industry. Industry-specific mutual funds will usually limit themselves to investing in particular industries. There are thousands of such funds.
Their focus can be very broad (such as technology - here) or very narrow (such as solar energy - here). Investors who would like to gain exposure to specific industries to round out their portfolios can do so with an industry-specific fund which offers diversification among many different holdings in an industry, as opposed to one or two stocks in an industry.
If an investor is not very educated about a particular industry, or does not have time to keep up with it, the fund managers at an industry-specific fund will take care of the decision-making and industry research.