Most of the ads in general, like in TVs or newspapers, are there to let you know about the product and the brand. You are not expected to buy immediately after seeing the ad. However, you will more likely prefer a brand or product you already know about when you buy something you are not familiar with.

I buy popular brands I see on ads often enough (especially if you consider food items). Granted, there was a reasonable chance I was going to buy the products anyway, but seeing the ad probably raised the chances. I think every time I thought about the product, there was a chance that I was going to pull the trigger on buying it, and seeing the ad prompted another thought about the product. Also, when I see ads, I often have a thought like "I see this ad more often than the competitor's ads. Are they doing better? Maybe it really is because their product is better than the competitor's".

Consciously.

Not very often, for me. I used to consciously avoid them.

Nowadays on search engines knowing that they're likely spending a dollar or two to reach me, I'll click to test the veracity of their targetting. If they're going to bid for people searching from X in country Y, they'll be needing an ROI and providing I'm genuinely interested in whatever X is, the ad is no problem.

Not consciously, perhaps.