This is the 16335th most frequent Russian word.
рекламодателям
"рекламодателям" means "to advertisers."
The word 'рекламодателям' is in the dative case, used to indicate the individuals who received the help.
Мы предоставили помощь рекламодателям в разработке их кампаний.
We provided help to advertisers in developing their campaigns.
Here, 'рекламодателям' in the dative case shows who is the recipient of the action, i.e., the intended audience of the writing.
Я писал рекламодателям, чтобы обсудить условия сотрудничества.
I wrote to advertisers to discuss the conditions of collaboration.
In this case, 'рекламодателям' specifies to whom the offers are being directed, again employing the dative case.