This is the 2119th most frequent Russian word.
сразу
"Сразу" means "immediately" or "at once."
The word "сразу" here means "immediately" and is used to indicate that the action of understanding happened without delay.
Я сразу понял, что это хорошая идея.
I immediately understood that this was a good idea.
In this context, "сразу" means "straight" or "directly" and conveys that there was no intermediate stopping or delay before going home.
После работы я пошел домой сразу.
After work, I went straight home.
The word "сразу" in this sentence implies an action did not occur "immediately" or "at the first attempt."