The following review is based on lectures given in the 1 ^ { st } Samos Cosmology summer school .
It presents an attempt to discuss various issues of current interest in Observational Cosmology , the selection of which as well as the emphasis given , reflects my own preference and biases .
After presenting some Cosmological basics , for which I was aided by excellent text-books , I emphasize on attempts to determine some of the important cosmological parameters ; the Hubble constant , the curvature and total mass content of the Universe .
The outcome of these very recent studies is that the concordance model , that fits the majority of observations , is that with \Omega _ { \mathrm { m } } + \Omega _ { \Lambda } = 1 , \Omega _ { \Lambda } \simeq 0.7 , H _ { \circ } \simeq 70 km s ^ { -1 } Mpc ^ { -1 } , \Omega _ { \mathrm { B } } \simeq 0.04 and spectral index of primordial fluctuations , the inflationary value n \simeq 1 .
I apologise before hand for the many important works that I have omitted and for the possible misunderstanding of those presented .