Renewal is when your annual pet insurance policy reaches its end date and you decide whether to continue it for another year.
Most pet insurance policies run for 12 months and then need to be renewed. Renewal isn't automatic in the sense that the terms stay the same. Quite a lot can change from one year to the next.
Premiums almost always increase at renewal, particularly as your pet gets older. What's less expected for some people is that the policy terms can also change. Conditions your pet has been treated for during the year may be excluded going forward, cover limits may shift, and the structure of the excess can change.
It's a policy detail to read your renewal documents properly each year rather than letting the policy roll over without checking what you're agreeing to. If the new terms or price don't suit you, you can shop around. But bear in mind that switching insurers means any conditions your pet has had will be treated as pre-existing by the new insurer, which may affect what's covered.
Continuous cover, renewing each year without gaps, is generally better than allowing a break, particularly for pets with ongoing conditions. A gap in cover can create complications around what a new policy will and won't include.