When renting a dedicated server from a provider you are granted exclusive use of the computer and everything that comes with it. The two main components of the service are - hardware (CPU, RAM, hard drives etc.) and a network connection. Initial OS installation is usually done by the server provider, any additional configuration can be done remotely using a remote access interface such as IPMI/KVM.
Renting out dedicated servers saves massive initial expenses on hardware, dedicated IP addresses and allocated bandwidth that can handle the irregular traffic of the internet. Furthermore, you usually have a team watching over the network and servers 24/7 that is prepared to act if anything goes sideways which means additional savings on manpower.
Bandwidth is the data transfer rate or the amount of data that can be transferred through the network in a fixed period of time. We usually measure it in bits per second. It is an important performance factor with dedicated servers as it determines how fast we can transfer data over a wired or wireless connection.
Remember not to mistake bandwidth with throughput. Bandwidth is the theoretical maximum of transferable data whereas throughput is the amount of actual useful data transferred through the network pipe. We can measure throughput with various tools, most commonly speed tests.
DDoS - Distributed Denial of Service
Is a type of cyber attack with the aim to render a website unavailable. Unlike a DoS attack, where a single internet connection is used to flood a target with fake requests a DDoS attack uses multiple connected devices distributed across the internet. These devices are infected with malware allowing remote access to the attacker. The target is overloaded with unwanted traffic causing it to shut down and become temporarily unavailable to its intended users. As this traffic originates from thousands of unique IP addresses it is very difficult to stop the attack with a simple IP block.
There are many ways of fighting DDoS attacks: software firewalls, hardware firewalls etc. However, these solutions are known to have their disadvantages, they can be costly, especially in the case of hardware firewall and despite their high price tag, they tend to be faulty (They can’t handle large volume attacks and frequent updates are necessary - DDoS attacks evolve every minute and it is difficult to keep up with the changes). What providers often choose instead, at least as a basic service, is 24/7 network monitoring and deep packet inspection. If any DDos attack occurs they locate the unwanted (infected) traffic and filter it out.