Draw Weight - in a crossbow, the amount of pounds force required to draw the string back the designed distance to the cocking mechanism. Can be measured with a scale or hanging weights or several other methods.
"Triggers" or 'actions' or 'cocking mechanisms' or 'locks' come in many types. Externally some look like a firearm trigger, some are a long lever under the tiller, others are thumb-activated on the wrist of the tiller. Two common relatively simple types are the Roller Nut and the Pinlock.
Bolts are fletched with pieces of leather, feather or wood which are glued and/or occasionally tied to the shaft. Many bolts only have two fletches .
LOTS of research material here. Use the Search feature. Also read the Crossbow Building Wiki.
After you've done some background research, let us know what kind and draw weight of crossbow you're interested in and we can point you to some more specific information.