Loratadine and cetirizine are both active ingredients in hay fever and allergy medications, and they both work as antihistamines.
Some people may find that loratadine medications are better at managing their allergy symptoms, whereas others may find that cetirizine works better for them.
Both are common, widely used antihistamines, so which one you want to use is entirely up to you and your own personal circumstances and medical restrictions, if you have any.