A block on a webpage is an HTML element that appears on a new line, i.e. underneath the preceding element in a horizontal writing mode, and above the following element (commonly known as a block-level element). For example,
<p> is by default a block-level element, whereas
<a> is an inline element — you can put several links next to one another in your HTML source and they will sit on the same line as one another in the rendered output.
display property you can change whether an element displays inline or as a block (among many other options); blocks are also subject to the effects of positioning schemes and use of the