The short answer
A conservation area is designated to protect architectural or historic character, often restricting external alterations.
Being in a conservation area doesn't stop you owning or living in a property, but it can significantly limit what you're allowed to change on the outside, from windows to extensions. Worth knowing before you buy with renovation plans in mind.
Why this matters for your purchase
Conservation area status is picked up in the planning constraints section of a PropM8 report, alongside the other designations that can limit what you're allowed to change.