Investing in a sector fund is a great way to gain exposure to a particular industry or sector of the economy. Sector funds are mutual funds or exchange-traded funds (ETFs) that invest in stocks of companies within a specific sector, such as technology, healthcare, or energy.
From Wikipedia
An index fund is a mutual fund or exchange-traded fund (ETF) designed to follow certain preset rules so that it can replicate the performance of a specified basket of underlying securities.