This is the 5194th most frequent Japanese word.
開けろ
"Open it" (command form).
The word '開けろ' is used here as a directive to perform the action of opening ('開ける') the door, presented in an imperative manner.
ドアを開けろと言われた。
I was told to open the door.
In this sentence, '開けろ' functions as a command, suggesting action to open ('開ける') the window to allow fresh air.
窓を開けろ、空気が新鮮だ。
Open the window, the air is fresh.
Here, '開けろ' directs to open ('開ける') the box, which is followed by an exploratory action to observe the contents inside.