Salesforce sObjects have a method called clone() which creates a copy of the sObject record. This method has four Boolean type optional parameters.

clone(preserveId, isDeepClone, preserveReadonlyTimestamps, preserveAutonumber)

Clone method parameters are as follows:

opt_preserve_id
Type: Boolean
Description: Determines whether the ID of the original object is preserved or cleared in the duplicate. If set to true, the ID is copied to the duplicate. The default is false, that is, the ID is cleared.

opt_IsDeepClone
Type: Boolean
Description: Determines whether the method creates a full copy of the sObject field, or just a reference:
If set to true, the method creates a full copy of the sObject. All fields on the sObject are duplicated in memory, including relationship fields. Consequently, if you make changes to a field on the cloned sObject, the original sObject is not affected.
If set to false, the method performs a shallow copy of the sObject fields. All copied relationship fields reference the original sObjects. Consequently, if you make changes to a relationship field on the cloned sObject, the corresponding field on the original sObject is also affected, and vice-versa. The default is false.

opt_preserve_readonly_timestamps
Type: Boolean
Description: Determines whether the read-only timestamp fields are preserved or cleared in the duplicate. If set to true, the read-only fields CreatedById, CreatedDate, LastModifiedById, and LastModifiedDate are copied to the duplicate. The default is false, that is, the values are cleared.

opt_preserve_autonumber
Type: Boolean
Description: Determines whether auto number fields of the original object are preserved or cleared in the duplicate. If set to true, auto number fields are copied to the cloned object. The default is false, that is, auto number fields are cleared.

Example:

Account acc = new Account(Name = 'Salesforce', Billingcity = 'Texas', Phone = '9999999999');
insert acc;    

//Cloning the above Account Record acc
Account accCloneCopy  = acc.clone(false, false, false, false);
insert accCloneCopy;