Я прячу подарок в шкафу.

• Прятать is the imperfective aspect. It describes an ongoing, habitual or repeated action (e.g. “I’m in the process of hiding…”).
• Спрятать is the perfective aspect. It describes the completion of the action (e.g. “I have hidden…”).
In our sentence Я прячу подарок в шкафу, the speaker focuses on the action as it happens (present tense, imperfective).

• Прячу is first person singular, present tense.
• The infinitive (dictionary) form is прятать.
Conjugation pattern for прятать in the present:
я прячу
ты прячешь
он/она прячет
мы прячем
вы прячете
они прячут

• Подарок is the direct object of the verb “to hide,” so it takes the accusative case.
• Masculine inanimate nouns have the same form in the accusative as in the nominative.
– Nominative: подарок
– Accusative (inanimate): подарок

• After в (and на), the accusative expresses motion toward (“into the wardrobe”).
• The prepositional expresses location (“inside the wardrobe”).
Since прятать here describes placing the gift somewhere (a static location), we use в шкафу (prepositional).

• The standard prepositional ending for masculine nouns is -е (e.g. о доме).
• A small group of masculine nouns (especially those denoting parts of buildings, containers, etc.) use a special locative ending -у after в/на.
– шкаф → в шкафу
– завод → на заводу (dialectal/poetic)

• In modern standard Russian, в шкафу is the correct locative after в.
• В шкафе is an older or dialectal form and is rarely used today.
• The meaning remains “in the wardrobe,” but for everyday speech and writing you should use в шкафу.