立刻 and 马上：
Both these words have the meaning “immediately”, “at once”, or “right away”, and they are both used as adverbs of time. However, they have an important difference.立刻means “immediately”, “right away”, or “right now”, so it’s normally used in situations when the circumstances are very urgent.
Therefore, it contains a sort of command mood. So when something will happen or has to be done in the next second or next minute we use 立刻, but 马上is more used in situations that allow a short delay.