Dear Lois T.
[Is that your real name?]
Deep down towards the bottom of your brain there's a big bundle of nerve cells called the hippocampus.
The hippocampus helps you remember things, including the 'landmarks' that are around you at any particular moment. For instance, if you are using a computer and leave it to go and get a drink in the kitchen, information about where the computer is and what familiar places you have passed on the way to the kitchen will be stored in your hippocampus. This 'memory of place' works all the time and only gets confused when you have been asleep for a long time or you are moving very fast in an unfamiliar environment--like on a rollercoaster, for instance.
As well as that, like most other animals, humans have a collection of little nerve cells (or neurons) called 'header cells'. Each cell becomes active when your head is in a particular position. This is necessary so you know which way you are facing so that you can coordinate the information your brain receives from your eyes and your ears. Probably the 'map' information in the hippocampus combines with information from the header cells and lots of other pictures you have in your head to give you a clear idea of where you are.
That's the best that I can explain it. But please note that scientists don't know much about this yet and it might turn out that some of the things I have written are wrong.
In the meantime, I hope this letter finds you...wherever you are!
Yours sincerely