Supreetha J
Standard initialization takes the values defined by the user for the solution variables and initializes the flow field to these values. This is the recommended approach for advanced simulations such as those involving porous media. 
Hybrid on the other hand, provides a slightly more realistic approach by imposing a non-uniform initial guess. In this method, a Laplace equation is solved to determine the velocity and pressure fields, and all other variables are automatically patched, based on domain-averaged values or a predetermined interpolation approach. This is the default initialization method in Ansys Fluent and works well for a wide range of problems.  
For more information, do check Initializing the Solution section of Ansys User’s Guide 32.9. Initializing the Solution (
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Hope this helps!