In this discussion, number refers to a counting number: $\,1\,$, $\,2\,$, $\,3\,$, and so on.
The factors of a number are the numbers that go into it evenly.
For example, the factors of
$\,10\,$ are $\,1\,$, $\,2\,$, $\,5\,$, and $\,10\,$.
The factors of
$\,42\,$ are $\,1\,$, $\,2\,$, $\,3\,$, $\,6\,$, $\,7\,$, $\,14\,$, $\,21\,$, and $\,42\,$.
Notice that factors occur in pairs:
$1\times 42 = 42$
$2\times 21 = 42$
$3\times 14 = 42$
$6\times 7 = 42$
Every number has a factor of
$\,1\,$, because $\,1\,$ goes into everything evenly.
Also, every number has itself as a factor.
Thus, the number
$\,1\,$ has only one factor—itself.
Every other number has at least two factors—itself and $\,1\,$.