When you host a site on a server, it works by using the server's shared IP address - a unique number which is used to detect a device connected to the Web. The website name that you use for the site is for easy access and convenience of the website visitors, but on a lower level, their web browser connects to the IP of the server. Considering that there're far more websites than IP addresses, shared website hosting servers use the same IP for many different websites even in case they are owned by several users. Even though this doesn't affect your website performance directly, having a dedicated IP may slightly improve the loading speed of a given website, giving it better rankings in search engine results. Such an IP is necessary for the installation of an SSL certificate as well, so when you would like to protect the payment or login details that your website visitors type in, you will need an IP together with the SSL.