Web Hosting (also called hosting & shared hosting) is one real server where allocated resources are shared between websites i.e. users via some cPanel interface etc.
A Dedicated Server is reserved exclusively for the account and usage of a single user. Whereas web-hosting plans, put many client accounts on a single server, space is enough but RAM is limited and this poor downs the performance of websites as soon they start to become successful.
Users of dedicated server has exclusive rights to the server’s bandwidth, memory and storage space; performance is not affected by traffic and usage patterns of other users.