Every part made by every manufacturer has one or more data sheets that accompany it. Those data sheets contain a wealth of information about the operating characteristics of components, operating voltages, maximum currents, etc...
Usually, the latest datasheet can be downloaded from several locations -- the manufacturer's websites, the distributor's website, etc... But occasionally you will run across a part that has a datasheet you must request from the manufacturer after signing a non-disclosure agreement.
"In recent years, marketing departments have been influencing the datasheets in a process referred to as specmanship - where data is cherry-picked to positively influence customer behavior. It is sometimes necessary to contact manufacturers directly and ask for additional information to ensure your part will behave as expected in your operating environment."