It is a hosting that is free, but your website is then placed for example an advertisement. This type of hosting is also not very reliable. It has more frequent outages and you can't turn to support too much. It is only suitable for projects and websites that you are not too serious about. For example, there is a risk of deleting the site without further notice (if the administrators think you may have violated some terms and conditions).
Probably the most famous Czech free hosting is Webzdarma.
