For the first one, I can tell you that from where I live (north of Mexico) I've never used or heard the word cristalera. One example with "ventana" would be: -Abriré la ventana porque hace calor. I will open the window because it is hot. For the second one: "mueble", that means furniture, is used more as a common or informal word. *in the furniture store* -Mira, me gusta ese mueble. Look, I like that piece of furniture. or -No se donde acomodar este mueble en mi habitación -I don't know where to put this piece of furniture in my bedroom. While, "mobiliario" is used more as a technical word, like in furniture jobs, and also can be used as singular and plural as well. -La mudanza se llevará el mobiliario del apartamento the moving company will take the furniture or -Es mucho mobiliario el que tiene esa tienda It is a lot of furniture that that store has. and the words "estante" y "repisa", both have the same meaning and are used in the same way. -El libro esta sobre la repisa. The book is on the shelf. -El estante es grande y pesado The shelf is big and heavy.