Common terms used in watch descriptions

Movement - the timekeeping mechanism of the watch, which is placed into the watch case for protection.  Most American movements were made in one of five standard sizes, 18, 16, and 12 were generally used in men's watches, and 6 and 0 sizes were used in ladies watches.  It is possible to have two cases that look like they are the same size, and find that the movements inside them are different sizes.  Generally, as time has passed, pocket watches have gotten smaller.
Sizes - I will list the movement size and the case size, the case size will be the outer diameter of the main round part of the watch.  As watches have gotten smaller over the years, some early pieces that were thought of as ladies sizes when new, now could be considered small men's, and some ladies will think that they are too large for a woman to wear.
Open face watch - with this watch you can see the face, or dial without opening it up
Hunting case watch - these watches have a metal cover over the dial and crystal to protect it, so that the front of the watch often looks just like the back.  To open it up to check the time, press the winding crown down, and the cover will spring up.  When closing, it is very important that you also again press down the winding crown, then push shut the cover and release the crown - it is possible to 'snap' shut the cover, but this will wear away the catch that holds it closed, and it will then no longer stay shut.
Lever setting - this is a method of setting the hands, there is a little lever at the edge of the dial that is pulled out away from the dial, then when the winding crown is turned the hands can be adjusted.  Slide it back in and then the watch can be wound up.
Pendant setting - the most common way of adjusting the hands, pull the winding crown out, and rotate it and the hands can be set, push it back down when finished Keywind/ key set - the watch is wound and set using a key
Crystal - the glass that covers the dial or face of the watch, sometimes these are plastic, but most of the watches here will have the old glass
Bow - the round hoop over the winding crown used to hang the watch on a chain