What is tickrate?
In computer games, unlike reality, time is quantized. This means that you can not choose any instant of time to perform an action, but you have to wait for a concrete one. In a Source server, a Tick is a scene generated by the server, that is, the position and location of the players and objects at a given time. To give the sensation of movement, it is necessary to generate one Tick after another at a minimum speed. Thus, the Tick rate indicates the number of scenes generated by the server in one second. The higher this value, the more powerful a processor will be required. The difference in processor consumption between a tick rate of 33 and 66 is triple. The modification of this value only concerns the consumption of processor and not the bandwidth.
When setting the Tick rate, what we do is limit a maximum of ticks per second. This means that if at any moment the processor is not able to generate all the ticks per second that have been imposed the server will automatically lower the Tick rate by adapting it to the specific conditions and the capacity of the processor, avoiding that it reaches 100% its use. If the tick rate drops below 10 fps, there will be lag on the server. With a higher number you can play normally.