An important challenge of cosmology is to understand the late time acceleration of universe. High precision cosmological observations in last decade suggest that about 73% of our universe’s energy density is in so called "Dark Energy". There are various models to describe dark energy. One of them is through Scalar fields. In my talk I will discuss about the Tachyon Dark Energy. Another way to explain the current epoch of accelerated is by modifying gravity at large scales. In the past few years, several schemes of large scale modifications have been actively investigated. I will also discuss about the F(R) gravity model and Galilean gravity.