A Systematic Investment Plan (SIP) is a vehicle offered by Mutual Funds to help you save regularly.
It allows you to invest in a MF by making periodic investments (fortnigthly, monthly or quarterly) instead of a one-time investment. For e.g. SIP allows you to pay 12 periodic investments of Rs. 500 each in place of a one-time investment of Rs. 6,000 in a Mutual Fund.