Can someone explain - or point me in the direction of

why the following selector is formatted how it is

tr.data th .description

I understand that the first part we are targeting data classes in the tr selector - but there is no space between the tr and .data (i get that)
but to target the description class in the th selector that is a child of tr - why is there a space between the th and the .description

what should i be searching for as a topic to help me understand how this works

Thanks

Here’s a link: Chaining CSS selectors

Thanks very much -

so am i right in thinking that the particular theory behind this is as follows

selecting all of the class of description that is a child of which is a child of all with a class=“data”

is that correct?