HTML

HTML - Hyper-Text Markup Language

Tags are the choice of elements that you wish to include into your webpage, such as <b> or </a>
The start and end tags both count as SEPARATE tags, which is important to remember.

Elements are the full form of the tag, with the start tag, content and then the end tag, for example;
<b>Insert some important information here</b>
This would be an element, as it contains both the opening and closing brackets, and also content.

Nesting is a way in which you can use more than one set of tags for one piece of content, such as possibly making a set of text bold, but also give it some spacing from the other content on the webpage.
<p><b>This piece of text is very important and should be read first</b></p>
The important thing to note here, is that the tags cannot overlap eachother, if one set of tags are inside another, then the inside one must be ended FIRST.

Attributes are what extra information is included within tags to help make them work, such as hyperlinking another webpage;
<a href=“http://karl-soft131.blogspot.com”>Next Page</a>
The href="http://karl-soft131.blogspot.com" is the attribute. To put it simple, it's the extra piece of information to help understand the purpose of the tag.
Alternatively this could also be used for inserting an image
 <img src=“Beach.jpg” />
As you can see here, src="Beach.jpg" is the attribute in this element.