i got a laptop for university and was told that it would be a good idea to get and external hard drive for it but i have no idea which one to buy. my laptop is an HP pavillion notebook
Pretty much anything from a known manufacturer such as Iomega, Seagate, Western Digital. You can get cheaper - but when you're relying on it, it doesn't make sense to scrimp. As it's a laptop, portability will be important so you may want to find one that's powered from the USB port - although I think those are typically only for smaller size drives. If your laptop supports USB 3.0, look for that in a drive - data transfer will be much faster.
If you can afford it, btw, get two - and back up one to the other every so oftem if what you're storing is important to you.
I don't know about other makes but if you have a Western digital drive on or attached to your system you can get a free cut down version of Acronis clone software.If it's saving work lot's of options including e-mailing it to yourself,another idea go to Amazon and look up clickfree this just saves your data rather than cloning your drive.
Most external drives now will be USB3 (backwards compatible with USB2 just slower).
For a laptop you need a 2.5 inch drive for portability. I would suggest a WD Mypassport (has built in backup software essential for Uni work).