This is the 5233rd most frequent Russian word.
обо
"About" or "concerning" (used before certain pronouns).
In this sentence, the word 'обо' is a preposition used with the pronoun 'всех' to mean 'about,' indicating consideration or thoughts regarding all friends.
Я думаю обо всех своих друзьях.
I think about all my friends.
Here, 'обо' is used as a preposition combined with 'всём,' indicating the topic of discussion encompassing everything.
Мы говорили обо всём вчера.
We talked about everything yesterday.
In this context, 'обо' is applied to the pronoun 'мне,' expressing concern or care directed at the speaker.