The amount of space you are allowed to store on your webhosting server is call Webhosting space. This is usually measured in GB (Gigabyte).
Let me simplify GB for you:
High quality photo taken from your iPhone or Android: Usually takes 1Mb-2MB
1000 MB = 1 GB
This would give you an idea about how much space 1 GB offers. Usually a simple blog post with 5-6 good quality images is not more than 4-5 MB (Extreme case).
For example, if you are uploading an image on your blog, which is of, size 1MB, it means you will be consuming 1MB of your web-space. Usually this size is huge and you can host a huge number of files on your server. For hosting WordPress blogs, I recommend you to purchase hosting from that webhosting company, which offers unlimited hosting space.
Another most common used term in webhosting is bandwidth. Bandwidth is the amount of data transfer allowed for your hosting. For example, if you upload an image of 1MB and one of your readers open that blog post, he will be consuming minimum 1MB of your bandwidth. Similarly if 100 readers read the same post, your total bandwidth consumption will be 100MB. Usually for a new WordPress site I suggest you to buy hosting from companies that offer either unlimited bandwidth or relatively high bandwidth usage (ex: 200Gb, 500GB).
cPanel is a webhosting control panel which offers graphical interface to manage your server. It’s because of cPanel that you will be able to manage your webhosting server without much technical skill. The graphical interface makes it easier to do various tasks like Installing WordPress, adding or deleting files, creating new FTP users and so on. cPanel is one of the standard control panel you will find in all the shared hosting.
Here is an image that illustrates cPanel: