Using \\[<dim>] in tabular environment

In a tabular environment what does \\[<dim>] do? Does that set the font size for the following line or for the current line? See example below?

\begin{tabular}{| c | c |}
words & more words \\[6pt]
stuff & other stuff \\
\end{tabular}
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Change 6pt to 50pt, its pretty clear what it does. – Nicholas Hamilton May 4 '14 at 13:00
It adds 6pt of vertical space below the row. – egreg May 4 '14 at 13:00
Thank you. What is the default then? – Maggick May 4 '14 at 13:01
@maggick Just use \\ – egreg May 4 '14 at 13:02