tomodati ha tosyokan de pasokon wo tukaimasu.

In Japanese, は marks the topic of the sentence (“as for my friend”), indicating what the sentence is about.

• は sets the scene or context.
• が marks the grammatical subject, often used to introduce new information or to emphasize who is doing something.
  Here, since the friend is already known or assumed, we use は to state what they do.

The particle で marks the location where an action takes place.

• 図書館で means “at the library.”
• You can think of で as the equivalent of “at” or “in” when describing where you do something.

The particle を marks the direct object of a verb, i.e. what is being acted upon.

• パソコンを使います literally means “use a computer.”
• を tells us that “computer” is the thing receiving the action “use.”

Japanese often omits possessive pronouns when context makes ownership clear.

• If you need to specify, you can say 私の友達は… (“my friend…”).
• But if it’s obvious from conversation or situation, you don’t need a pronoun.

Japanese nouns do not change form for number.

• 友達 can mean either “friend” or “friends,” depending on context.
• Here, without additional context, it could be one friend or multiple friends.

パソコン is a loanword (from “personal computer”).

• Japanese uses katakana for foreign words and onomatopoeia.
• Native words use hiragana or kanji; borrowed words go in katakana.

The ます-form is the polite or formal present/future tense.

• 使います = polite “use.”
• The plain (dictionary) form is 使う; you’d use that in casual speech or in writing like diaries.