While choosing to host, your first concern is “how much data you can store?”. For small websites, several gigabytes should be enough. Many hosts offer “unlimited storage” that is not actually “unlimited”. Their term and conditions indicate that this unlimited is limited up to the normal site use. So, if you need a big website talk to your host and set clear data storage limits.
Amount of Bandwidth
It is the amount of data that can be uploaded or downloaded per month by you and your user cumulatively. For instance, if the bandwidth in your package is 10 MBs; you have created a website by uploading 1 MB data; one user serf across your whole website and downloads the same one MB then you can only have 8 more such users in the said month.
After that your web hosting either would not allow more visitors or would charge extra per MB. Thus, carefully telly the provided bandwidth with your website requirements.