Hi!
CatAppPhotos is my first online project.
  in this course I learned basic HTML syntax.
I did this step by step in the freeCodeCamp.
here is the list of concepts that I got familiar with:
1-**How to create FORM**
2-**Practicing to code SEMANTICALLY.**
3-the fact that HTML has several semantic elements that define the different parts of a web page:
<header> - Defines a header for a document or a section
<nav> - Defines a set of navigation links
<section> - Defines a section in a document
<article> - Defines an independent, self-contained content
<aside> - Defines content aside from the content (like a sidebar)
<footer> - Defines a footer for a document or a section
<details> - Defines additional details that the user can open and close on demand
<summary> - Defines a heading for the <details> element
4- what is HTML element,tag.
5-how to tell the browser to parse the markup into multiple languages by creating a meta element as a child of the head element.
6-self-closing tag.
7-HTML attributes.
8-how to open link in new tab.
9-how an item can turn to a link by <a> tag.
10-<main>: which its a tag declare the 'main' part of the site.
11-got familiar with lists.
12-<figure> tag.
13-understand that it is important to keep elements in same line.
14-<meta> tag.