Difference between 'with sharing' and 'without sharing'?

Hi Mohit,

Without Sharing: the code runs in system context; all records and fields are available for use.Sharing rules are not applied for the current user.

With Sharing: the code runs in user context; DML operations may fail because of sharing settings, and queries will only return values available to the user.sharing rules for the current user are enforced

System Context: the code has full access to all records and fields in the system.

User Context: the code can only access records (and possibly fields, such as executeAnonymous calls) available to the user.