The situation you are facing is that the DNS record for your domain has not been set yet. Therefore it is still pointing to the Godaddy placeholder.
If you obtain a domain, you get access to its DNS settings. All registrars I know provide the domain with a DNS A record of a placeholder page. This A record points to the IP address of the server that is to handle the response.
Your 000webhost page is on a different IP than the IP known in the DNS settings, thus the domain name resolves to a different server (different IP address).
In order to have the domain name resolve to the new server you can do two things:
- Change the A (and AAAA for ipv6) record so it points to the correct server. This would be your ip on 000webhost.com.
- Change the nameservers. The nameservers are the servers that resolve the domain name. Basically your domain is probably know at two different nameservers (assuming you entered your domain somewhere in the 000webhost.com admin panel). So godaddy has a nameserver where your domain points to their servers, but 000webhost.com also has a version that points to their servers.
If you change nameservers from godaddy's to 000webhost's. Your domain name will be resolved by 000webhost and the A record will point to the correct IP address.
Option 1 will likely work as well, but will only route web traffic and you'd need to set other DNS settings for email etc. By changing the nameserver it is likely 000webhost will set those records for you as well and therefor it is easier.
Since 000webhost clearly states in their FAQ you should be changing the nameserver to theirs, I'd go for option 2.