question about AD lab

what does it mean?

[acrosstheuniverse]

Hi. i'm searching about AD lab. There are so many interesting functions in ad lab. but this isn't my field. so i have a trouble understanding something. here are my questions. if you have an answer, please reply me!

<entity association graph>

1) dataset types : within queries, within sessions.
>> what does 'sessions' mean? i think queries are keyword written by user in search window. am i right?

2) edge types : co-occurrence. MI scores.
>> i want to know the difference between those two.

and, AD center is for advertiser. not for provider. right? (like adwords)

waiting for your reply : ) thank you.