Ahahahaha! You thought I was complain about lag, didn't you? No. I am going to explain the different types of lag, what causes them, and how you can tell one type from the other. Server Lag - This type of lag causes block lag (blocks not breaking/placing quickly), mobs moving slowly or not reacting quickly, or chat being slow. This is the fault of the server's host; sometimes the host cannot keep up with all the things going on, and it starts falling behind. This can be caused by a ton of entities in one small area (mob farms not killing fast enough, items dropping on the ground and not being picked up, etc.), people spamming chat too much, or a ton of chunks being rendered quickly. Note that the aforementioned causes of server lag can also cause client lag on weaker computers if the player enters a particularly crowded area of entities. Client Lag - This type of lag is the cause of low fps, slow typing speed, and some visual glitches. This is caused by the player's computer/laptop not being powerful enough to render and display everything it currently has running, either due to a low quality graphics card or an overworked processor. Connection Lag - this one is less common and a bit trickier to single out, but it is the cause of seeming pauses in mobs, only for them to then seemingly fast-forward through time, hit you a dozen times, and so on. This type of lag is caused by a bottleneck in the internet connection between the player's computer/laptop and the server's host location. I hope this quick guide helps out people who are confused as to what is causing lag for them. I'm going to be honest here, more times than not, it's probably client lag.