Like in English, when you say "You come home". (= you come at home)
(But if you say "You come from home", in English you need the preposition "from")
Grammatically, in "you are home", or "you come home", "home" plays the role of an adverb.
Domo: ablative of domus.
"Ablative of place from which describes active motion away from a place.
Used with ab/ā/abs, "from"; ex/ē, "out of"; or dē, "down from".
For example, ex agrīs, "from the fields"; ex Graeciā in Italiam nāvigāvērunt, "They sailed from Greece to Italy."
Cities and small islands, as well as the word domus, use this ablative even without a preposition: Athēnīs discessit "he departed from Athens".
When it's used with "in": in +ablative.
It means a position, without the idea of moving:
In poculo (= in a cup, the wine is in a cup)
In pavimento (on the floor, there's something on the floor).
And: Domo (without any preposition): "From home"
Friendly warning: Please do NOT confuse the Latin ablative "ex agrīs" with its Ancient Greek cognate "ἐκ του αγρού " which is governed by the genitive.
I know it's been troubling everyone -- and most are embarrassed to come forward-- so, I thought I would just let everyone know you're not alone in this ! We've all been suffering and together we can pull through.
Benigne facis! Ego convictus est.
"the accusative of place to which"
"In Latin, nouns in the accusative case (accusativus) can be used:
(1) as a direct object;
(2) to indicate direction towards which e.g., domum,
"homewards"; Romam, "to Rome" with no preposition needed; this is known as the accusative of place to which, and is equivalent to the lative case found in some other languages.
[i found this link interesting. Thanks ! ]