Web hosting is the place where all the files of your website live. It is like the home of your website where it actually lives. Picture this, if the domain name was the address of your house, then web hosting is the actual house that address points to. All websites on the internet, need web hosting. The websites files are stored in online servers which are owned by hosting companies.

For a start a client or a potential website owner has to pay a website developer who will design and develop the website. The fee is usually a once payment fee depending on the agreement between the website developer and to be website owner. Sometimes the developer can charge a fee for mantaining and updating the website. THen the website owner has to pay for domain name and hosting. These can be paid monthly, quaterly or yearly.

Normaly yes they come with own e-mail accounts. As to how many e-mail accounts your hosting company gives you it will depend with what packages you paid for and these differ with Hosting companies.

Yes you can change hosting providers and still keep your domain name. One can also buy a domain name from one provider and choose to host with a different hosting provider.