What do 'Delimiter' and 'InheritsFromParent' attributes mean in .vsprops files?

<UserMacro Name="INCLUDEPATH" Value="$(VCROOT)Inc"
    InheritsFromParent="TRUE" Delimiter=";"/>

<VisualStudioPropertySheet ... InheritedPropertySheets=".my.vsprops">

...
<UserMacro Name="NOENV" Value="B"/>
<UserMacro Name="OVERRIDE" Value="B" PerformEnvironmentSet="true"/>
<UserMacro Name="PREPEND" Value="B" PerformEnvironmentSet="true"/>
...

...
<VisualStudioPropertySheet ... InheritedPropertySheets=".b.vsprops">
<UserMacro Name="ENV" Value="$(NOENV)" PerformEnvironmentSet="true"/>
<UserMacro Name="OVERRIDE" Value="D" PerformEnvironmentSet="true"/>
<UserMacro Name="PREPEND" Value="D" InheritsFromParent="true"
    Delimiter="+" PerformEnvironmentSet="true"/>
...

...
<Configuration ... InheritedPropertySheets=".d.vsprops">
<Tool Name="VCPreBuildEventTool" CommandLine="set | sort"/>
...

...
ENV=B
OVERRIDE=D
PREPEND=D+B
...