What does this mean when my teacher wants me write description of single day ?

Far be it from me to know your teacher's intentions, but I think any day can be expressed through major events. To make events more memorable for writing, I categorise them, might help you so I'll list a few. Transportation - there's always some highlight to a bus ride, though much less in school). Work / education - there are always plenty of details, and cramming is not particularly eventful, but each day there's some takeaway worth noting if you pay attention and have preferences. Leisure - random websurfing, learning new things in articles, webcomics, tv series & movies, gaming progress. Social interactions - gossip's likely more interesting to people, could also include pets, reflections on these and things that affect your mood. Ideas - random thoughts that sound cool, introspection, memories that have surfaced.