The supplication that we recite before we conclude the prayer continues with the words, ومن فتنة المحيا والممات translated as, “and from the trials of life and death.”
The word used for life is محيا a variation on the more common word for life: حياة. But the term محيا is more emphatic and expansive in its meaning, for it can apply to not only to the action or state of life, but also the time and place of it. When used in an Islamic framework, it is used specifically for human life, with the implication that it is being contrasted to death.
And such is the difference also between الممات meaning ‘death’, and the more common word for it: الموت, which can be used to refer to both humans and non-humans. The word الممات however, is used specifically for humans, and always with the implication that it is being contrasted to life - in fact, in the Qur’an, they are always mentioned alongside one another.
So when we take refuge in Allah from the trials of life and death, we are essentially asking Allaah to protect us from being testing in our religion while we are alive, to not allow us to fall into sin after being obedient, and to not allow us to go astray after being guided. And also to protect us from being tested at our death, from being questioned in the grave to the punishments that come after.