What is archiving?

public class ActionDTO extends GenericDTO implements Serializable,Auditable { // default serial version id, required for serializable classes. public static final String ACTION_SUSPEND = "SPN"; public static final String ACTION_DEREGISTER = "DRR"; public static final String ACTION_REINSTATE = "REI"; private static final long serialVersionUID = 1L; private Long actionId; private long accountId; private Date actionDate; private String actionType; private String remarks; private AccountDTO account; public ActionDTO() { } public ActionDTO(Long accountId, String action, String remarks, String updatedBy) { setAccountId(accountId); setActionType(action); setActionDate(new Date()); setRemarks(remarks); setUpdatedBy(updatedBy); } public Long getActionId() { return this.actionId; } public void setActionId(Long actionId) { this.actionId = actionId; } public long getAccountId() { return this.accountId; } public void setAccountId(long accountId) { this.accountId = accountId; } public Date getActionDate() { return this.actionDate; } public void setActionDate(Date actionDate) { this.actionDate = actionDate; } public String getActionType() { return this.actionType; } public void setActionType(String actionType) { this.actionType = actionType; } public String getRemarks() { return this.remarks; } public void setRemarks(String remarks) { this.remarks = remarks; } // bi-directional many-to-one association to AccountDTO public AccountDTO getAccount() { return this.account; } public void setAccount(AccountDTO account) { this.account = account; } @Override public String toString() { // TODO Auto-generated method stub return null; } } what is the purpose of @Override public String toString()...and what will do here ?