What is the difference between Internet with a capital I and the Internet?

Answer 1

internet with capital 'I' refers to the Internet as in the world wide web, and what most people think of when you say internet.

Internet with a lowercase 'i' refers to a bunch of small LANS connected together to form some kind of host-to-host packet delivery service. So basically Internet capital I refers to inter-networking at the global level. Whereas internet with a lowercase 'i' refers to it on a much smaller level.

Answer 2

No difference.

a capital letter.

That's true nowadays but previously they were different:

"The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite (TCP/IP) to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks of local to global scope that are linked by a broad array of electronic and optical networking technologies." (Wikipedia - Internet)

"The words internetwork and internet is [sic] simply a contraction of the phrase interconnected network. However, when written with a capital "I", the Internet refers to the worldwide set of interconnected networks. Hence, the Internet is an internet, but the reverse does not apply. The Internet is sometimes called the connected Internet." (IBM's TCP/IP Tutorial and Technical Overview)

Answer 3

Although both internet and Internet serves the same functions but the range of serving the function is different. internet with small i is for communication between 2 or 3 networks . Internet with capital i denotes communication between thousands of interconnected networks.