\bigskip & \medskip & \smallskip

Synopsis, one of:

\bigskip
\medskip
\smallskip

Produce an amount of vertical space, large or medium-sized or small. These commands are fragile (see \protect).

Here the skip suggests the passage of time (from The Golden Ocean by O’Brian).

Mr Saumarez would have something rude to say to him, no doubt: he
was at home again, and it was delightful.

\bigskip
``A hundred and fifty-seven miles and one third, in twenty-four hours,''
said Peter.

Each command is associated with a length defined in the document class file.

\bigskip

The same as \vspace{\bigskipamount}, ordinarily about one line space, with stretch and shrink. The default for the book and article classes is 12pt plus 4pt minus 4pt.

\medskip

The same as \vspace{\medskipamount}, ordinarily about half of a line space, with stretch and shrink. The default for the book and article classes is 6pt plus 2pt minus 2pt.

\smallskip

The same as \vspace{\smallskipamount}, ordinarily about a quarter of a line space, with stretch and shrink. The default for the book and article classes is 3pt plus 1pt minus 1pt.

Because each command is a \vspace, if you use on in mid-paragraph then it will insert its vertical space between the line in which you use it and the next line, not necessarily at the place that you use it. So these are best between paragraphs.

The commands \bigbreak, \medbreak, and \smallbreak are similar but also suggest to LaTeX that this is a good place to put a page break (see \bigbreak & \medbreak & \smallbreak.