What it means
代わりに means “instead of” or “in place of.” It presents a replacement, substitution, or alternative: one person or thing takes the place of another, or one action is chosen instead of another. It attaches to a noun with の and to a verb in its plain nonpast form. The construction can be used in both familiar and polite sentences; the register is shown by the rest of the sentence, not by 代わりに itself.
Usage note
With nouns, の is required before 代わりに. With verbs, use the plain nonpast form, including before a polite main clause. Depending on context, 代わりに can also mean “in return” or “as compensation,” so the surrounding sentence determines whether it expresses substitution or an exchange.
How to use it
父の代わりに、私が会議で報告します。
Instead of my father, I will give the report at the meeting.
私は車を使う代わりに、駅まで自転車で行きます。
Instead of using a car, I go to the station by bicycle.
父の代わりに、私が会議で報告する。
Instead of my father, I will give the report at the meeting.
私は車を使う代わりに、駅まで自転車で行く。
Instead of using a car, I go to the station by bicycle.