In Bohr's model I studied that energy of an electron in the $nth$ shell is given by:
$$E_{n}=-13.6 × \frac{Z^2}{n^2} eV.$$
Clearly, the energy of the electron comes out to be negative. But what is the meaning of negative energy? What is its significance? What is the negative sign trying to tell us? Please can someone explain? I am so confused. Please help.