Explain yourself

SELECT * FROM gallery2 WHERE topic_id="397311" UNION SELECT * FROM gallery2 WHERE topic_id="1792570" UNION SELECT * FROM gallery2 WHERE topic_id="170545" UNION SELECT * FROM gallery2 WHERE topic_id="1368200" UNION SELECT * FROM gallery2 WHERE topic_id="833948" UNION SELECT * FROM gallery2 WHERE topic_id="1799148" UNION SELECT * FROM gallery2 WHERE topic_id="1333611" UNION SELECT * FROM gallery2 WHERE topic_id="491656" UNION SELECT * FROM gallery2 WHERE topic_id="481177" UNION SELECT * FROM gallery2 WHERE topic_id="931189" UNION SELECT * FROM gallery2 WHERE topic_id="496990" UNION SELECT * FROM gallery2 WHERE topic_id="738793" UNION SELECT * FROM gallery2 WHERE topic_id="1246759" UNION SELECT * FROM gallery2 WHERE topic_id="1547268" UNION SELECT * FROM gallery2 WHERE topic_id="134077" UNION SELECT * FROM gallery2 WHERE topic_id="62564"