Power series don't have to be centered at $0$. They can be
centered at any point $a$, in which case the series will contain powers of $(x-a)$ instead of $x$. If a power series centered at $a$ has radius of convergence $R$, its interval of convergence will be from $a-R$ to $a+R$.
Example: The power series $$\displaystyle{\sum_{n=1}^\infty \frac{(-1)^{n+1}(x-1)^n}{n}}$$ is centered at $a=1$. It has
a radius of convergence of $1$, and an interval of convergence of $(0,2]$. (This series adds up to $\ln(x)$, by the way.)