Unlimited hosting? Companies usually advertise these plans, they dont limit you on data transfer nor on disk space. But still there are some restrictions..
For storage (disk space) you cant for example use hosting as a data storage, all files must be part of the website. Also usually you cant exceed like 100K files hosted or similar limits..
For data transfer, they limit you on bandwidth, meaning you cant for example transfer 30MB per second whole month.
But if unlimited hosting is bought from reputable company, then it can be good choice i think.