A user is a person who browses the internet (or other things) using a device. Users usually use the internet without much knowledge about it. Along with users there are also power users, people who can use advanced features of programmes which are not normally used by the average user.
An ISP, or Internet Service Provider is an organisation that provides the service of the internet for customers. ISPs might be commercial, non-profit or even private. ISP's are used to access and use the internet.
A webpage is information that gets put together from html, (a coding language) to something on the internet a user can view and interact with. A webpage can also be useful for a company to show off it's products. To connect to a webpage you need to go on to the World Wide Web (which is on the internet) and type in the URL (uniform resorce locator) where you will be taken to the page. Webpages are also what make up websites.
The World Wide Web is a way of getting information over the internet. The World Wide Web is an 'an information space' where webpages can be visited via URLs. The Web; as it is commonly referred to, uses HTTP to share it's information and let me clarify, it is not the internet.
Modems are objects that broadcast Wifi throughout a centralised area such as a house or an office, not unlike a router would. This piece of hardware takes one (or more) radio signals and decodes them for whomever wants to view the information.
A network is the thing that a device connected to the internet interacts with. It can be used for a variety of things; from sending an e-mail to making a website. Networks are computers which are all connected for the purpose of sharing information that practically anyone with internet access can use. Most networks serve to make it easier to share over the internet but some 'private networks' may exist within a company to make it easier to work with the company without other people interfering.
Fibre optic cables are cables (as the name implies) that function using threads of glass to transfer light as information. While being good for long distance travel with little to no signal loss, fibre optics are not the cheapest things to manufacture, needing the factories to make the tiny threads of glass and then transport them sometimes thousands of kilometers.