Look at the sentence: I will go home. Why is the preposition 'to' missing?
I will go to the bank.
She went to the gym.
These are correct, but "I will go to home" is wrong!
The answer is that in 'I go home', 'home' is an adverb. It is the direction of travel. This means it does not use the preposition 'to'.
In the example, 'She went to the gym', 'gym' is a noun (a place) and so we need the preposition.
You may think that 'home' is a noun, and it can be used as a noun. However, in 'I go home' you are using it as a direction of travel (homeward is the original, old English).
If you add a possession adjective (my, our, her, etc.) to 'home' then 'home' becomes a noun. Let's see:
I will go home. Home is being used as a direction of travel and so an adverb.
I will go to her home. Because 'home' is now a noun you need the preposition 'to'.
Let's look at some sentences where prepositions are not need:
I went home.
We went abroad.
You are going somewhere.
We have been underground.
She went anywhere.
It went inside.
All of the underlined words are adverbs of location and do not need prepositions.
Here is a list of all the 'places' that do not need prepositions:
underground
upstairs / downstairs
downtown
inside / outside
here / there
back
away / near / close
abroad / overseas
everywhere / somewhere / nowhere