This exercise is in the form of a diary entry.
In a ten-minute freewrite, describe a yesterday, or a day not too long ago, by using ONLY nouns (i.e. words for things or people).
This exercise is designed to give practice in observation and in using strong, specific description so aim to stick to concrete nouns (for example: “mushroom curry” “College Road” “Mike”) versus abstract nouns (such as “boredom” “beauty” etc).
A piece of writing like this is an excellent investment for the future if you are a writer because details are what makes fiction, poetry and memoir convincing and alive.
But never feel constrained by a prompt when freewriting. You can spend ten minutes describing your day using abstract qualities such as loneliness or loyalty if you want, and simply ignore the instruction to stick to nouns. The only rule is never to stop writing, even for a moment.
Go for it!