Highlighted search words in serp titles

Hello everybody ,
searching for "Costa Esmeralda Cerdena" on google I noticed that some page titles show those search words in bald and in other page titles they are not .
I suppose it is a new thing because I never noticed that before .
Any reason why this is happening ?
Thank you from italy

It's not new. If you always search in quotes you may not have seen bolding as often. Take off the quotes and you will see it a lot.

The reason there is only one listing that is bolded when you type in "Costa Esmeralda Cerdena" is because there is only one listing near the top that has the exact match (combination and order of words) of your query.

Take off the quotes and you will notice different combinations of those words bold with several words between throughout description, titles, and content snippets. This is a broad match.
Excuse me if I am using AdWords terminology.

I am sure there is an older search term that describes this more technically (boolean?). Any classic search linguists out there care to educate us?

I do not use quotes with searchwords that often , that is why it puzzled me . Thank you , I have taken in now .
Uh, your concern about terminology is wasted with me :-)
I'm a total beginner !

I think if you use quotes you can get more accurate results on your search term and the results display the whole word that you type on the search box. But if you want to see your ranking I agree that you must remove the quotes because most of the user don't use quotes.