Strictly speaking, a terrarium originally referred to a planted enclosure built around live vegetation, closer to a small indoor garden than a housing unit for an animal. A vivarium, by contrast, technically refers to any enclosure built to house a living creature, whether that's a
Reptile Centre Northampton, amphibian or invertebrate, with or without live planting. In practice, though, UK retailers and keepers use both terms fairly loosely, often depending on regional habit or supplier naming rather than any strict definition.
This doesn't mean every component has to come from the same supplier forever, once a setup is established and a keeper knows what works. But for a first setup in particular, where the cost of getting it wrong is a stressed animal and a return trip to sort it out, one supplier and one checked list tends to be the simpler route.
Sizing tiers are the other area worth understanding before buying. Ranges like VivExotic's are usually grouped by length and depth rather than by a single headline dimension, and the right tier depends on the adult size of the species rather than how it looks as a juvenile. Buying a vivarium sized for an adult from the outset, rather than upgrading later, tends to work out simpler and cheaper overall.
Ventilation is where a lot of wooden vivariums are quietly let down. Front ventilation panels, usually built into the door frame, allow airflow without letting heat and humidity escape too quickly, which matters more for species that need stable humidity than it does for very dry-adapted ones. Checking where the ventilation sits, and how much of it there is, tells you a good deal about which species a given vivarium was designed around.
Anyone new to reptile keeping quickly notices that the words vivarium, terrarium and enclosure all seem to describe more or less the same thing, and get used almost interchangeably across the UK pet trade. That overlap isn't a mistake exactly, but it does confuse more new keepers than it probably should, so it's worth untangling.
Temperature and humidity checks matter more in these first 48 hours than at almost any other point, since this is when a keeper finds out whether the vivarium set up before the animal's arrival is actually holding steady under real conditions. Checking thermostat readings against a separate thermometer, ideally at both the warm and cool ends of the enclosure, confirms the setup is doing what it's meant to before the animal has been in it long enough for a problem to become serious.