As defined by the U.S. Patent and Trademark Office (U.S. PTO).
Intellectual property (I.P.): Creations of the mind—creative works or ideas embodied in a form that can be shared or can enable others to recreate, emulate, or manufacture them. There are four ways to protect intellectual property: patents, trademarks, copyrights, and/or trade secrets.
Patent: A property right granted by the government of the United States of America to an inventor "to exclude others from making, using, offering for sale, or selling the invention throughout the United States or importing the invention into the United States" for a limited time in exchange for public disclosure of the invention when the patent is granted.
There are three types of patents: utility (what the invention does); design (how the invention looks); and plant (a distinct and new variety of plant).
Examples: sports bra; CAPTCHA (website security program); Super Soaker water gun.
Trademark: Any word, phrase, symbol, design, or a combination of these things that identifies the source of goods or services. Businesses and individuals use trademarks with their goods or services so that customers recognize them in the marketplace and distinguish them from competitors.
Examples: Coke Zero; Vaseline; Pampers
Copyright: The U.S. Copyright Law protects original works of authorship, such as writings, music, and works of art. Copyrights may be federally registered with the Library of Congress through the U.S. Copyright Office.
Section 107 of the Copyright Act outlines the factors to consider whether the reproduction or other use of a copyrighted work qualifies as "fair use". Works that are no longer protected by copyright are in the "public domain" and may be used freely without the permission of the former copyright owner. Every January 1 is observed as Public Domain Day in the United States. (U.S. Copyright Office; Britannica.com; Center for the Study of Public Domain)
Examples: movies; photographs; computer software
Trade secret: Information that companies keep secret to give them an advantage over their competitors. This will be information that is not generally known; a company/individual will make reasonable efforts to maintain secrecy.
Examples: manufacturing processes; detailed ingredients for a food product; chemical composition of a drug
A History of Intellectual Property in 50 Objects by 
Scientific Authorship: credit and intellectual property in science by 
Science, Colonialism, and Indigenous Peoples : the cultural politics of law and knowledge by 
Making and Unmaking Intellectual Property: Creative Production in Legal and Cultural Perspective by 
The color of creatorship : intellectual property, race, and the making of Americans by 
Special Topics in Intellectual Property by Are you an inventor, artist, or designer? If so, you may have intellectual property that might need protection.
The I.P. Identifier can point you in the right direction just by answering a few questions.