There's no such thing as a free lunch, economists say. The meaning behind this adage is that is impossible to get something without paying something in exchange. When it comes to 000Webhosting, this observation doesn't apply. If you choose their services, you won't have to pay anything, and as is the case with other hosting services, your websites won't be displaying ads in exchange.
The salient points are : 1500MB for disk space, a C-panel look alike, 100 GB/month for data transfer, 5 email addresses, 5 domains (actually subdomains name-of-your-site.webii.web, for example).
In my personal experience the websites I made experienced little trouble, but they were not very "heavy" and were mostly for experimentation purposes. My websites were down a few times, and a few more I couldn't reach the servers. So, I wouldn't really recommend them for professional purposes or for something serious. 000Webhost provides very reasonable service if you want to create your own website for personal purposes or if, say, your children's chess club need a website. It can be perfect for a society or a club, or if you're a student.