Hey please dnt give wrong answers ...

whenever a build is released first of all we do smoke 
testing to check whether the build is ready to take further 
testing.its just to check the major funtionality ..

Sanity testing is in depth testing which cover all the 
major and minor functionality of a project..

for e.g let to check module A , B , C is called smoke 
testing than in depth testing of these modules like in <A> 
a1,a2,a3.. than in function <B> b1,b2,b3 ,i mean in depth 
testing of major functionality,is called sanity testing..

in sanity we dnt need to execute test cases..