Two Tomtar. In english Tomtar is called Elfs, but it's not really the same thing. In the Nordic countries, there is a myriad of different folklore creatures called "Oknytt".
Tomten is perhaps one of the few that some people still believe in, at least a little. Although very few would openly admit so.
A very short description of the Tomtar. Just like humans, they are mortal. However, they live very long lives, perhaps 300-400 years. They also have some magical abilities. Most notably, the ability to turn invisible. They can also make their home invisible.
A Tomte is the protector and caretaker of a place. You can be certain that every old farm has one or several Tomtar looking after the place, even if it is abandoned. You can also find Tomtar in churches, castles, graveyards, barns and cottages. In fact, there is probably a Tomte in every building. Even newer ones.
Tomtar also resides in the forests. If a stretch of road running through or near a forest and has more accidents than usual then Tomtar may be the cause. They are probably angry at the traffic. Despite this, Tomtar are usually good and helpful as long as you do not anger them. If you do, they can be very vengeful.
Some things you absolutely should avoid if you want "your" Tomte to stay friendly:
Never throw out hot water without first shouting a warning to the Tomte
Never forget to give porridge to the Tomte on Christmas
Never destroy large rocks or trees on your land unless you really have to. The Tomte will know if it was absolutely necessary or not.
Lastly, as I'm a nurse, I want to add that it is very common for people with dementia or mental disorders to start seeing Tomtar, or "smågubbar" meaning little people. It's so common that it has become a proverb. To say that someone is seeing "smågubbar" is to say that they are a bit crazy. It would be interesting to hear if this is the case in other places as well or if it is something specific to the Nordics.