Answer
It means that the sum of an infinite series
$\Sigma^{\infty}_{n=1}a_{n}=a_{1} + a_{2} + a_{3}...$ is $5$.
Work Step by Step
$\Sigma^{\infty}_{n=1}a_{n} = 5$
It means that the sum of an infinite series
$\Sigma^{\infty}_{n=1}a_{n}=a_{1} + a_{2} + a_{3}...$ is $5$.
So $\lim\limits_{n \to \infty}S_{n}=5$ where $S_{n}$ is partial sum.