understanding of code

Can someone explain the meaning of this code in detail

 v_email_cd := TRIM (SUBSTR (i_email_cd, 1, INSTR (i_email_cd, i_locale) - 2));

SELECT b.resource_id, c.resource_id
                 INTO v_email_cd_res_id, v_email_subject_res_id
                 FROM (SELECT resource_id
                         FROM rbm_key
                        WHERE resource_code = (SELECT TRIM ('MESSAGE.BODY.' || SUBSTR (i_email_cd, 1, INSTR (i_email_cd, i_locale) - 2))
                                                 FROM DUAL)) b,
                      (SELECT resource_id
                         FROM rbm_key
                        WHERE resource_code = (SELECT TRIM ('MESSAGE.SUBJECT.' || SUBSTR (i_email_cd, 1, INSTR (i_email_cd, i_locale) - 2))
                                                 FROM DUAL)) c;