Notebook entry is the page that you can write about your daily activities. Something about your friends or a brief information about yourself. It is very useful page to practice your writing skill. If you are learning a language, native speakers of that language will correct your notebook entry.

it's your italki journal.

As Sewwandi said an entry in a notebook :) Write notebook entries so that you can practice your English. That way people can correct you on any grammar, spelling etc and you will learn from your mistakes and improve :)

an entry in a notebook