The RFC 791 says :
The internet protocol does not provide a reliable communication facility. There are no acknowledgments either end-to-end or hop-by-hop. There is no error control for data, only a header checksum. There are no retransmissions. There is no flow control. Errors detected may be reported via the Internet Control Message Protocol (ICMP)  which is implemented in the internet protocol module.
My questions :
- give an example when the header checksum is set to 1
- 'Errors may be reported' what does that mean ? How it decides which errors it should report and which not ?
Thank you in advance! Note that I am not a college student so if you throw some weird words please explain what they mean.