So, let’s say you’re inside the nucleus of the atom. When we are talking about 1S orbitals, or even just about orbitals, we are considering the electron not as a particle but as a wave. Consider for example waves like in the sea. It’s hard to really say where is the wave right? Same is for an electron: it’s not really possible to say there or there is the electron. what you do can say is that certain spots or locations are more likely for the electron to be. For the 1S orbital, which forms a sphere around the nucleus, the radius of this sphere is the bohr radius. On this radius, the electron has the highest chance to be.