Professional references are people whom you worked with, preferably for at least six months in recent years. Usually an ex-supervisor and up to managing directors are chosen to act as a reference. In contrast, personal references are non-colleagues who can attest to your character and perhaps work ethics. If the type of references is not specified, you can assume that it is the business references that may interest the employer more.
The answer is always yes. You may even want to ask the person in person if possible. The convention is to use someone whom you have worked with recently. Needless to say, you want to be pretty certain that the reference will speak well of you. And do not forget to express your gratitude after the fact, and especially if you got the job.
Employers may call your references and have a chat with them about you. Big corporations may outsource this to other companies specialized in the task.
Most people can find at least a couple of people to use as a reference. But if you have just come of age or had a long employment gap, adding someone that you have worked on a volunteer basis can also be a viable option. If you do not have any volunteer experience, perhaps a former teacher who remembers you would be willing to attest to your character and learning abilities.
A letter of recommendation is a personal note written by one person, not just a contact to reach out to. It is often used in college application in addition to job hunting. If you have an esteemed former co-worker who is willing to write a letter of recommendation, it may just close the deal for you in some instances.