Calibre (Caliber) refers to the specific model or design of a watch movement, encompassing the arrangement and functionality of its components.
Calibre (European spelling) or caliber (American) refers to the specific movement design used in a watch, identified by a manufacturer's designation number. The term historically referred to the size of a movement (from French, derived from Arabic qālib meaning 'mould'). Today it identifies both the movement's dimensions and its specific design iteration. Rolex Calibre 3235, Patek Philippe Calibre 324 and ETA Calibre 2824-2 are examples that specify exact movement models.
An in-house calibre is designed and manufactured by the watch brand itself. An ébauche is a partially completed movement blank bought from a specialist movement maker such as ETA, Sellita or Soprod, then finished, decorated and adjusted by the watch brand. Many respected brands use modified ébauches. Fully in-house movements carry more prestige and higher prices, but a well-finished ébauche-based movement can be just as reliable.
Yes, significantly. In-house calibres from prestigious brands command premiums and affect collectibility. Common movements like the ETA 2824 are easy to service worldwide at lower cost. Proprietary calibres may require factory service, and discontinued calibres can be costly to service due to scarce parts.