These are all based on the settings for FDI on your AMD. The details can be found here https://community.dynatrace.com/community/display/...
But in general to answer your question, here are the default reasons
Data Center - The operation exceeded the threshold and server time was more than 50% of the operation time. Effectively it took the server a long time to respond. This could either be the server in question or it waiting for another resource deeper in the delivery chain.
Client/ 3rd Party - The operation exceeded the threshold and idle time was more than 50% of the operation time. Effectively this is where during the operation execution when there is no network or server activity related to the operation. This could be a number of things, client machine is busy processing, components are requested from another server or components are being cached further out from the server in question.
Network Other - Is slightly different. Firstly it classifies it as being slow for network which is the threshold for the time the network (between the user and the server) takes to deliver requests to the server and to deliver page information back to the user. In other words, Network time is the portion of transaction time that is due to the delivery time on the network.
Once this is done it then checks to see why the network is slow and breaks that cateogry down into one of the following
Network - Latency - RTT is causing the deterioration of Operation Time.
Network - Loss Rate - Loss Rate is the reason for degradation of Operation Time
Network - Other - Neither RTT or Loss Rate thresholds are breached but the network time threshold was.
Hope that makes sense.
The three major categories correspond to the various tiers that components a mapped to in DCRUM. Here is a link in the documentation that provides a quick overview on how DCRUM defines those tiers (https://community.dynatrace.com/community/display/DCRUMDOC/Applications):
Client Network: Represents network segments between all user locations and monitored infrastructure
Network: All other network segments, primarily data center network infrastructure
Data Center Tiers represents the primary metric (Performance by default) and other important KPIs over time for all Data Center tiers for a selected application or transaction, as defined by the CAS administrator.