Eyepieces are needed for observing. Depending on the focal length, you achieve a certain level of magnification.
The specification 1.25" refers to the diameter of the connector (1.25" = 31.8 millimetres).
A telescope always displays an object upside down. This law of optics can only be compensated for by an erecting system. Erecting lenses, diagonal mirrors or Amici prisms provide you with an upright image. Diagonal mirrors provide an upright but back-to-front image and Amici prisms provide an upright and right-sided image.