We have considered nonlinear systems whose line dependence is deterministic and Fwesent~d some n:;pre,,~ntaive physical ~y:;tems whk:hrndisplay chaotic behavior. Simple model maps which can exhibit chaos slmitarrnto the chaos observed In more complex system" are studied. Characterizationrnfor one dimensional maps whether they are chaotic or not are given quantitatively.rnThe three known prominent scenarios, and their accompaning experiments,rnleading to chaos are analysed in some detail. StranDe attractors in dissipativernsystems and their relevance to turbulence is considered. ihernappearance of chaos in conservative systems are shortly d,~alt. Finally,rnchaos In different bf'aIYJw; of science and its implications are stated