Huawei P series are flagship smartphones with the best cameras. However, they usually have lower-quality displays, slower processors and graphics chips than Huawei Mate series.
Huawei Mate are also high-end phones, like the P series, but they have inferior quality cameras.
Huawei Y series are low-end smartphones. What is most noticeable are the displays of much lower quality than the P and Mate series.
Honor Series is a separate brand belonging to Huawei founded in 2013. Manufactures mid-end phones.