Negative exact blocks one precise search term and nothing else. Negative phrase blocks any search containing that word or sequence of words in that order, so it removes a whole family of searches at once. Use negative exact for individual proven losers, and negative phrase for entire categories of wrong intent — but check what else a phrase would catch before applying it.
What each one actually blocks
Negative exact on 'dog bowl stand' stops that search alone. 'Dog bowl stands', 'stand for dog bowl' and 'dog bowls stand' all remain live, and in practice sellers regularly see those near-variants continue to spend.
Negative phrase on 'stand' stops every search containing the word stand, in any surrounding wording. That is what you want if stands are not your product, and exactly what you do not want if 'water bottle that stands upright' is one of your converters.
Where to apply them
A negative applied at ad group level covers only that ad group. Campaign-level negatives cover every ad group in that campaign.
If spend on a term continues after negation, the most common explanation is that it is coming from a different campaign entirely.
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