DO YOU NEED PHP FOR PERSONAL BLOG?

yup: https://www.ads-software.com/about/requirements/

1. Please. don’t yell – all caps are considered yelling ??
2. Yes. Read the requirements: click About the the top and then the link on the left.

So, do I have to install WordPress, or does my host?

Hosts usually do NOT install it for you (unless you pay them). However, they might offer some installation script (like Fantastico, Elefante etc.) – but that depends on the host.

yeah, it is rare that hosts also service installation of any PHP applications. some will make them available to you or say they suppot them, but as far as installing them – this is your responsibility.