Explicite selection

A plotting style is usually selected using the with keyword, like

plot x with points

This allows to use different plotting styles for every plot:

plot x with points, 2*x with lines

Typing help with in the gnuplot command window gives a list of all available plotting styles.

Global plotting style selection

Plotting styles can also be set globally for all plot commands. Here, gnuplot distinguishes between function and data plots, for which different default styles can be set.

For functions use set style function:

set style function linespoints
plot x, 2*x

For data files use set style data:

set style data lines
plot 'file.dat', 'other-file.dat'

Note, that for functions the default style is lines, and for data files it is points. With show style data and show style function you can inspect the currently selected plotting styles.