Short answer: updates, security checks, and periodic performance reviews, ensuring the score you receive upon delivery remains consistent.
A website is not a product but an installation: it ages if left unattended. Plugins receive updates, WordPress receives security patches, and pages that load quickly today become slower as more content is added.
What the maintenance includes:
- Updates of WordPress, themes, and plugins — tested before going live, not implemented blindly
- Security: monitoring and backups, ensuring there is always a way back
- Speed: periodic measurements, as load times tend to creep up
- Visibility: checking if pages remain indexed and ensuring no links are broken
The latter is the part that is most often skipped and costs the most when things go wrong.