DNS 101 Miniseries #5 - Why do we need DNSSEC
DNSSEC strengthens authentication in DNS using digital signatures based on public key cryptography. With DNSSEC, it's not DNS queries and responses themselves that are cryptographically signed, but rather DNS data itself is signed by the owner of the data.
This video steps through what benefits DNSSEC provides and one of the common attacks which can be conducted against DNS.
Other videos mentioned are in this section of the course, you can access them directly.