So.. think of your group of friends. Ever notice how some of them are always opposed to what the group wants to do? If everyone decides to order pizza, they think tacos are the way to go. Maybe they're vocal about this, or maybe they quietly disagree so as not to make waves and start a fight. During the American Revolutionary period (ca. 1770-1785), the patriots fighting for independence also had those friends with contrary desires.
At that time in the colonies, you either wanted independence from Britain, or desired to stay under their control. Those against independence were called loyalists because they were loyal to Britain. Also called Tories, they were opposed by patriots, who wanted independence. Like that pesky few in your friend group, loyalists were sometimes hard to pin down because they feared speaking up and earning retribution.
And who were the loyalists?
Since their founding, the American colonies were under British control. Great Britain wanted to expand its empire throughout the world, so they established colonies anywhere they could. Over time, many in the 13 colonies (what would become the United States) started rumbling for independence, rather than having some monarchy 3,000 miles away telling them what do to.
But not everyone wanted this freedom. Many people were happy with status quo and felt there was no reason to forcefully oppose actions of the British government. If anything needed to change, it should be done peacefully. They believed if people were to take up arms or riot, that would lead to a terrible situation with mob rule and no control. Think of your group of friends again, and what happens when they fight over what to do -- sometimes, everyone picks sides and gets angry with each other, and you end up at home in the basement watching reruns. Not fun.
Loyalists who wanted to maintain the support of Britain weren't the loudest and most outspoken group, save for a few examples, so their exact number is unknown, but generally ranges from one fifth to one third of colonists. Not exactly a majority.
Many Patriots, who were opposed to Great Britain, served in the Continental Army
Patriots
Though small in number, loyalists were diverse and lived everywhere. A blacksmith, a merchant, a minister, African Americans thinking Britain would free them, Native Americans; the list goes on. Some simply supported Britain. Others actually took up arms and fought as guerrillas (think special forces) against the Continental Army, as some from New York did.