1.what is the difference between systematic investment plan and equity linked savings scheme?

This is required for next year’s tax planning purpose.In case of opening SIP now what is the benefit and whether it will be more beneficial to open Equity linked savings scheme??Whether in the ELSS(equity linked savings scheme) a bulk amount has to be deposited??Any fixed period is there?
Whether rate of interest is market driven??Whether it is beneficial to invest in it when the stock market falls?