Bandwidth
Bandwidth is the maximum capacity of the data transfer in one second through communication medium. Generally, bandwidth can also be defined as the difference between higher frequency range to lower frequency range of signal during data transmission. It is used to refer to analog signal which includes the field of digital communication, wireless communication, signal processing and so on. Here, we are going to discuss about bandwidth and its relative terms.
Expression of Bandwidth
Bandwidth has different expression for computer networking and radio signal. For computer network, bandwidth is expressed in bps (bit per second) and its higher terms such as Kbps (Kilo bit per seconds), Mbps (Mega bit per second) and Gbps (Giga bit per second). In this era, we use internet having bandwidth in Mbps range whereas bigger company use that of in Gbps range which are relatively faster than bps and Kbps. For radio signal, it is expressed in cycle per second (Hz) and its higher terms such as KHz (Kilo Hertz), MHz (Mega Hertz), GHz (Giga Hertz) and so on. Consider, a signal having maximum range of 250 Hz and minimum range of 150 Hz, then the bandwidth of the signal will be 100 Hz.
Bandwidth vs Speed
Sometimes, people think that bandwidth and internet speed are same things. But they are different from one another. Suppose, our ISP (Internet Service Provider) provides 25 Mbps bandwidth but our internet speed never reaches up to 25 Mbps because internet speed is affected by various factors. Basically, internet speed is actual rate of data transfer through our communication media. Many ISPs allow some limitation in bandwidth for uploading and downloading. Internet traffic, connection protocol, distance and capacity of the wires are the major factors affecting of internet speed.
Bandwidth in web hosting
Bandwidth in web hosting is the amount of data which can be transferred between a website and computer/mobile connected to it within a specific time. Generally, it is calculated in monthly packages by website hosts. But, some of them provide unlimited bandwidth. It is easier to understand how bandwidth works, it can be taken as a width of pipe. A wider pipe can transfer more water at a time than that of a small piper because of more capacity of the wider pipe. In similar manner, more bandwidth means more amount of website data can be transferred at a time.
Devices and their Bandwidth
Each of the internet accessing devices have their own bandwidth. Several devices available in the market that are capable to transfer data from Kbps to Gbps range. They are designed to solve our problem related to internet connection. Most of us use Ethernet cable which has bandwidth of 10 Mbps. Some of devices and their respective bandwidth are shown in given picture.

How much bandwidth do I need?
If there are multiple devices and several members who uses internet in your family, then you need to have high bandwidth internet. Sometimes, we are facing the problem of lagging during gaming and other activities. It is necessary to select certain suitable bandwidth for streaming HD video, gaming and other purpose which provides best experience. According to FCC (Federal Communication Commission), we must have at least 25 Mbps bandwidth internet for 4K videos. The following picture indicates how much Mbps bandwidth is needed for respective purpose.


Source: https://www.fcc.gov/consumers/guides/broadband-speed-guide
Solution for Bandwidth Problem
If we face the problem of slow internet speed, there are various ways to enhance our connection effectively. First of all, we should troubleshoot the problem, so that, we can get the reason of problem. We have to install the best download manager on our mobile/computer to manage and download files properly. If nothing works, then we should buy internet of higher bandwidth as per needed. Analyzing and monitoring the network bandwidth performance regularly helps us to keep away from such problems.