There are two main types of web hosting.
Free host allows you to host without paying bill per month or yearly basis.
Best for experiments:
Free hosts provide a good environment to experiment different webmaster techniques. You can learn and experiment many things before switching to paid hosting.
Placing Ads and Banners on your website:
Free doesn’t means free at all. You have to pay something in return. Mostly free hosts put ads and banners on your websites to generate revenue. You have no control on quality of ads and placement.
Free hosts cannot offer rich features. Usually they have limited features because of poor revenue model.
There is no guarantee or quality of services in free services. Servers can go down for week or days, no one is answerable to you. There is no support department to help you in technical problems. Free hosts can close the services at any times leaving you clueless.
In this type of service you have to pay the bills at the end of month. Because of high competition in hosting industry it is very affordable to host any website. Now you can host a business website or personal blog in $3 to $7 per month.
Reliability and Stability:
Paid hosts offers reliable services. They are responsible for server failure or any technical issues. Good web host offers 99.9% uptime guarantee to your website. In case of technical issues, you get sufficient help from technical support. Paid hosting service offers rich features combined with quality of services.
You have to pay bills to paid service providers.