What are the top tips for online advertising?

Question

contextual advertising

Good day, forum users! I have a few questions for you. Could you tell us the basic principles and the most effective online advertising channels? And what a trick in Yandex direct, that a separate page is needed for each product. That is, for example, I create an ad with pictures of buckwheat / pasta / milk, and when a client clicks, it should be redirected to a separate page of this product (this is allowed). And if it is redirected to the page of the store with a window for this product (this is prohibited), what is the logic? Is it like this everywhere or only in Yandex? Because from all points of view, the window with the product outperforms a separate page (even in terms of the transition - I went in, saw the product in the window, closed it and look at other products). Here is an example of a window: instamart.ru/metro/makarony-makfa-pieria-liubitielskiie
ps I also wanted to know where to buy ads using an example - I went to any site on the network and in the window (yes even the same skype) there is your ad, what is it called and where is it bought? How about the cost?
Thanks in advance!