What are unit trusts,mutual funds and how does anyone invest or gain from them?

what are the diferences between them? and what are pyramid schemes? what is multi level marketing?

Unit Trust: A regulated investment company or mutual fund, especially in the United Kingdom. It is an open-end collective investment vehicle that offers investors diversification and professional management. [Bloomberg]

Mutual Fund: An investment company that pools individual, institutional and other investors' money and invests it in a variety of securities or markets. Shares can be redeemed at Net Asset Value (NAV). The funds offer investors diversification and professional management for a management fee (usually calculated on a daily basis). [Bloomberg]

Pyramid Scheme: A fraudulent money-making scheme in which people are recruited to make payments to others above them in a hierarchy while expecting to receive payments from people below them. Eventually, the number of new recruits fails to sustain the payment structure, and the scheme collapses with most people losing the money they paid in. [Bloomberg]

Multi-Level Marketing: A sales system under which the salesperson receives a commission on his or her own sales and a smaller commission on the sales from each person he or she convinces to become a salesperson.
[http://www.investorwords.com/3154/Multi_...

Investing in mutual funds is relatively easy. Most major funds can be purchased directly from the fund company. Go to the website (e.g., Vanguard), download the prospectus and follow instructions.