Getting started with jquery-selectors – Installation or Setup

1 Tag Name
Represents a tag name available in the DOM. For example $('p') selects all paragraphs <p> in the document.

2 Tag ID
Represents a tag available with the given ID in the DOM. For example $('#some-id') selects the single element in the document that has an ID of some-id.

3 Tag Class
Represents a tag available with the given class in the DOM. For example $('.some-class') selects all elements in the document that have a class of some-class.

All the above items can be used either on their own or in combination with other selectors. All the jQuery selectors are based on the same principle except some tweaking.

NOTE − The factory function $() is a synonym of jQuery() function. So in case you are using any other JavaScript library where $ sign is conflicting with some thing else then you can replace $ sign by jQuery name and you can use function jQuery() instead of $().

Example
Following is a simple example which makes use of Tag Selector. This would select all the elements with a tag name p and will set their background to "yellow".

<html>

   <head>
      <title>The jQuery Example</title>
      <script type = "text/javascript" 
         src = "http://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>

      <script type = "text/javascript" language = "javascript">
         $(document).ready(function() {
            $("p").css("background-color", "yellow");
         });
      </script>
   </head>
    
   <body>
      <div>
         <p class = "myclass">This is a paragraph.</p>
         <p id = "myid">This is second paragraph.</p>
         <p>This is third paragraph.</p>
      </div>
   </body>
    
</html>

if you want to reproduce, please indicate the source:
Getting started with jquery-selectors – Installation or Setup - CodeDay