The "processor" (also called the CPU) is the beating heart of a laptop. In the same way the human body relies on the heart to make it work, the laptop requires a processor to make it work.
The better the processor the faster the laptop will work and the more it can do.
HP is a decent make, but the processor on this model is pretty poor. However if all you are going to do is internet, email it will be fine.
£300 is about the low end for laptops, and with this laptop you are getting what you pay for.