What are Persistent Cookies and Cookies?

'Cookies' is the word which I have been listening and nodding my head about it for a year but I never knew what it is and what does it do on a computer? Hopefully, I have up to now known that cookies are related to networking and browsing and nothing else. Could anyone help me about the functions of the cookies on a computer and the disability of a computer in the absence of cookies. Are there cookies in all browsers?
