Why root makes phone fast I have heard many sites saying that  rooting makes phone faster but in technical detail it just increase process and more process = slow phone so why people say it 

Example : we have phone   A  and phone  B   A  is rooted and  B  is not but   A  runs without any root apps so which will be fast (according to sites A will be fast)
There are several ways that having root may improve performance. But just rooting won't make a phone faster.


One common thing to do with a rooted phone is to remove "bloat" apps. These are apps that are installed by default. In recent versions of android, you can "freeze" or "Turn Off" more built-in apps, making root less of a requirement for de-bloating. Here's a guide for those without without root. With root, your best bet is to find a guide in the specific forum for your phone on XDA Developers or a similar site. These will include other users' experience about what is safe to remove or disable. 
There used to be a lot of types of apps that could tune the memory management with the goal of improved performance or longer battery life, but I haven't seen them recently. Modern phones often have a lot more ram (2 or more GB) than they used to. 
Another thing that a rooted phone with a specific kernel can do is overclock the processor. This is complex and potentially dangerous (could crash or cause physical damage to the phone by overheating), but may be useful for older phones with slower processors. 
Installing a custom ROM may also make the phone run faster, depending on a lot of factors about the specific phone and the specific ROM. 
There are also many specific fixes for individual phones that can improve performance. 
Ad blockers can speed up web browsing (as well as make the phone more secure). Most of these require root as they install hosts redirects, although there are some that appear as a VPN and should work without root.