Blogger tag are special tag used in Blogger Language. this tag identifiable by the prefix {b:}

The list of Blogger Tags

Tag Name	Description
<b:section>	The section tag is to split the theme into sections. These tags can only contain tags <b:widget>.
<b:widget>	Gadget tags are embedded in tags <b:section>. A gadget tag can only contain tags <b:includable>, one of them must have "main" as id.
<b:widget-settings> <b:widget-setting>	Gadget settings tags. These tags contain the settings of a Gadget and can only be used in a widget tag.
<b:defaultmarkups> <b:defaultmarkup>	This tag can create markup that can be called later. <b:defaultmarkups> is the main tag of the markup section, and <b:defaultmarkup> are the body part of markup, this tagcan only contain the inclusions tag <b:includable>.
<b:includable> <b:include/>	The tag <b:includable> is the inclusion, it divides the widget into one or more sections and the tag <b:include> calls for inclusion.
<b:if> <b:elseif/> <b:else/>	The Conditional tags. These tags contain an expression whose result is a Boolean value. The nested content will be executed or not depending on the statement result.
<b:switch> <b:case/> <b:default/>	Switch tags. These tags have a role similar to conditional tags, with the difference that the result is not limited to a Boolean value.
<b:with>	Variable aliases. Creates an expression that can be used in child nodes.
<b:loop>	Hold the data contained in a table.
<b:comment>	Comment tag, give comment or note to a block of code.
<b:tag>	Add tag based on certain condition.
<b:attr/>	Give attribute to parent.
<b:class/>	Give class to the parent
<b:message> <b:param/>	Take a word stored in the Blogger server based on Blog Language settings.
<b:eval/>	The expression evaluation tag. Used to display the result of an expression.
<![CDATA[]]>	Tell the compiler not to encode its content.
<data:.../>	The data output tag. Displays the value of the data of an expression.