What is the difference between the Search Network, Display Network, Shopping, Video and Performance Max campaigns?

They differ by where ads appear and, crucially, by intent.

• Search — text ads on Google results pages, triggered by keywords. The user is actively looking, so intent is highest and conversion rates are best. This is where most budgets should start.
• Display — image and responsive ads across millions of partner sites. Users are not searching, so it is a demand-generation and remarketing channel. Cheap clicks, low conversion rates, and easy to waste money on if you do not exclude poor placements.
• Shopping — product listings with image, price, and merchant, driven by a Merchant Center feed rather than keywords. Essential for e-commerce; the feed quality is what determines performance.
• Video — YouTube placements. Strong for awareness and consideration; measurable direct response is harder and needs realistic expectations.
• Performance Max — one campaign serving across every Google surface using automation, driven by asset groups and audience signals rather than keywords.

Note: Performance Max is the one interviewers probe on. The honest assessment is that it can perform well with strong conversion data and good creative assets, but it gives limited visibility into where spend goes and can cannibalise branded search. The practical advice is to add brand negatives, feed it high-quality assets and audience signals, and never run it as your only campaign type.