The idea of a negative-pressure dark energy component in the Universe which causes an accelerated expansion in the late Universe has deep implications in models of field theory and general relativity. In this article, we survey the evidence for dark energy from cosmological observations which started from the compilation of distance-luminosity plots of Type Ia supernovae. This turned out to be consistent with the dark energy inferred from the CMB observations and large scale surveys and gave rise to the concordance $Lambda$CDM model of cosmology. In this article, we discuss the observational evidence for dark energy from Type Ia supernovae, CMB, galaxy surveys, observations of the Sunyaev-Zeldovich effect from clusters, and lensing by clusters. We also discuss the observational discrepancy in the values of $H_0$ and $sigma_8$ between CMB and large scale structures and discuss if varying dark energy models are able to resolve these tensions between different observations.
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