How do I write and use the equivalent of serverside includes in Odoo? <  include virtual="/templates/footer.asp" >

I've stared for days at this code without getting a clue! https://stackoverflow.com/questions/41855895/how-to-include-in-odoo

Please help me to complete the following code to something that that I can understand and that actually works! :-)

[code]module.localID
website.layout
myModule.layout
<template id="mLayout">
    <div>Header</div>
    <t t-raw="0" />
    <div>Footer</div>
</template>
<template id="myModule">
    <t call="mLayout">
    ... code

   </t>
</template>[/code]