Checked exceptions should be taken care by the user using 
try and catch blocks otherwise runtime error occurs
for eg:
class.forName() method throws ClassNotFoundException which 
should be caught between try and catch blocks

Unchecked exceptions are taken care by the jvm itself, user 
need not worry about these type of exceptions
for eg:
Integer.parseInt() method throws NullPointerException which 
need not be placed between try and catch blocks

Checked Exceptions must be caught and thrown by the user
otherwise compile  time error will be displayed saying it
must be catched. We've to catch those exceptions using try
and catch blocks. 
Eg:Class.forName() throws ClassNotFoundException, when
trying to load the specified file in class.forName().

whereas Unchecked Exceptions are handled by jvm, user need
not to handle those exceptions.