Abstarct: In this thesis‎, ‎we study the cosmic EW and QCD Phase Transitions (PTs) and their effects on the Universe that we can see‎. ‎When the Universe was about 〖10〗^(-10)seconds old‎, ‎the EWPT‎, ‎in which symmetry between weak and electromagnetic interactions was broken‎, ‎occurred‎. ‎About 〖10〗^(-5)after the big bang‎, ‎the PT from the quark–gluon plasma to the hadronic phase happened‎. ‎In the early Universe first-order PTs can also generate Gravitational Waves (GWs)‎. ‎In this thesis‎, ‎we study the cosmological first-order QCD PT and for the first time calculate the GW spectrum of the bubble evolution with holographic models‎. ‎Using AdS/QCD and the correspondence between a first order Hawking-Page phase transition and confinement-deconfinement phase transition‎, ‎we find the spectrum and the strain amplitude of the gravitational wave within the hard and soft wall models‎. ‎We postulate the duration of the phase transition corresponds to the evaporation time of the black hole in the five dimensional dual gravity space‎, ‎and thereby obtain a bound on the string length in the space and correspondingly on the duration of the QCD phase transition‎. ‎We also show that IPTA and SKA detectors will be able to detect these gravitational waves‎, ‎which can be an evidence for the first order deconfinement transition. Consistent with cosmological constraints‎, ‎there are scenarios with the large lepton asymmetry which can lead to the finite baryochemical potential at the cosmic QCD phase transition scale‎. ‎In this ‎thesis‎‎, ‎we investigate this possibility in the holographic models‎. ‎Using the holographic renormalization method‎, ‎we find the first order Hawking-Page phase transition‎, ‎between Reissner-Nordstrom AdS black hole and thermal charged AdS space‎, ‎corresponding to the de/confinement phase transition‎. ‎We obtain the gravitational wave spectra generated during the evolution of bubbles for a range of the bubble wall velocity and examine the reliability of the scenarios and consequent calculations by gravitational wave experiments‎. Furthermore‎, ‎we discuss about the baryogenesis and the origin of the matter-antimatter asymmetry during these PTs‎. ‎We propose a new mechanism for electroweak baryogenesis baxsed on gravitational waves generated by helical magnetic fields that are present during a first order electroweak phase transition‎. ‎We generate a net lepton number through the gravitational chiral anomaly which appears due to the chiral gravitational waves produced by these magnetic fields‎. ‎The observed value of baryon asymmetry can be obtained in our mechanism within parameter space of scenarios with an inverse cascade evolution for magnetic fields which can also be candidates for large-scale magnetic fields.