When you create an ad, you will not select keywords, but you will also decide how exactly you want to match the users’ search query.
Broad match : This will let your customers see your ad if they enter searches that are similar to your keywords.
Exact match : Using this, customers will only see your ad if they enter the exact keywords or keyword phrases that you selected.
Negative Match : Using this option, you can select keywords that you don’t want your ad to be associated with. If these words enter into the search bar, your ads will not show up.