Interactive Photo Gallery I'am stuck a little bit

I'have a problem with instructions.

Instructions are to: " At the top of the page you'll have a search area where photos will hide and show depending on user input. When the user clicks on a thumbnail the photo will display in a lightbox. There should be a back and previous buttons to cycle through photos.".

I downloaded project files in the images folder, there are normal images and Thumbnails folder with Thumbnails images inside.

I've build the gallery with basic html css, I've added "lightbox" and "buttons which responds on mouse click and keyboard arrows" so far so good().

I checked the instructions again and saw, that I have to use the Thumbnails pictures to build the gallery instead of the normal ones(which I already used to build the gallery) and on user's click the normal pictures have to pop up in lightbox.

At least that's how I get the instructions, but now I am not sure which way is the desired one. If the second way is true I have to re-write the code. I'am asking for guidance how to proceed from now on.

There is another instruction which is not clear for me. Instructions are to: "Implement the search box at the top of the page that filters photos based on the captions. The photos should filter in real-time as you type. This could be a jQuery plugin that you find on the web, or code that you write yourself."

The unclear part is: Does the user have to write the whole caption sentence or to write some keywords in the search box, so the search box can filter the images acording to the input of the user. I guess that first one which is to "write the whole caption sentence" is irrelevant.

Thanks !