Every user on Blinkenshell gets a home directory at /home/<username> with a disk quota (storage limit). The quota depends on if it's a free or a supporter account. The home directory quota is used for all files stored, including web pages and email. Both free and supporter accounts have their home directories compressed by ZFS, which means you can on average store about 4.5x more data than the quota depending on what type of data you are storing.
If you compare file size outputs from the df command you can see it's less than when checking with the ls command. For example df might say 2 MB and ls might show 8 MB for the same file, this is because of the ZFS compression.