Switchports are tied to a back-plane or “fabric”, the back-plane coordinates switching between ports and end devices. Sometimes there is a discrepancy between the processing power of the back-plane and its switchports:
Say a consumer switch has five gigabit ports, that means that each port theoretically should be able to handle gigabit traffic, but can all five do so at the same time? Depending on the capacity of the back-plane a switch is either determined to be blocking, meaning that the back-plane will not be able to handle gigabit/full traffic across all ports simultaneously and blocks some traffic to keep up, or non-blocking meaning that all ports can send at full speed at the same time without problem.
Consumer devices such as most home switched are blocking because its unlikely a home user ever will use all switchports at full speed at the same time ever, by using a blocked switch fabric the manufacturer can lower the price of its devices which is an added benefit for home users.
Companies however, such as ISPs, data centers, etc will likely require full speed across all their ports so they can oversubscribe users to their services, essentially selling more speed than what is available, and in doing so require non-blocking fabric switches.
A good overview by Phil Anderson
Sources:
https://i.cs.hku.hk/~atctam/phdthesis/node25.html
https://files.fivemin.info/index.php/s/rEdTsPFzJsWcmX7
Example of non-blocking architecture
https://www.broadcom.com/products/ethernet-connectivity/switching/strataxgs/bcm56170