Applying css styles based on html element sequence - through a .css file

I am applying styles to my html elements from a style sheet.

I want to know what is the difference between

//No comma seperation
.elementSpace tbody tr td input label{ 
    margin-left: 0.5em;
}

and

//comma seperation between input and label
.elementSpace tbody tr td input, label{
    margin-left: 0.5em;
}