In the theoretical sense, bits are either 1 or 0. Physically, since computers work in electricity, this corresponds to a gain or drop in the amount of electrical energy associated with any given bit.
Information is moved from one computer to another by sending digital signals in a stream.
Any file transfer method has some chance of causing information loss. Electro-magnetic disturbances abound in the world and any of them can cause the hypothetical negative five volts to become positive five volts. This is a big problem, since any flip in the bits might dramatically change the final message. Bad information is no less destructive today. It is virtually impossible to perfectly shield bits in transit from electromagnetic interference.