also, too, as well, and even
도 is used after subject and object nouns to express the listing of subjects and objects or the addition of a subject or object to one mentioned previously. This meaning corresponds to 'also' or 'too' in English.
When added to a subject particle, the subject particle is omitted, leaving only 도.
Similarly, when added to the object particle, 을/를 is omitted, leaving only 도.
When 도 is added to particles other than subject or object particles, however, the other particle is not omitted.
It indicates that the noun is being added to a list of items, actions, or descriptions previously mentioned or understood from the context.
When combined with 은/는 (Topic) or 을/를 (Object) the 도 particle can replace them entirely, rather than appending to them.
In other cases, it functions as usual, adding its meaning without replacing any existing particles
10 more sentences in the app — free account.