Piplelines with and without Foreach cmdlet

A question about the pipleline and foreach

Say I have the below 2 patterns of PowerShell pipeline syntax:

cmdlet1 | cmdlet2 



cmdlet1 | foreach {cmdlet2} 

How do I intuitively decide which one among the above two to go for while addressing a problem?

For example, with get-content import-csv we use foreach cmdlet but with get-aduser and set-aduser we do not. My question is what is the science here that distinguishes the 2 usage patterns.



Hope my question makes sense.

Thanks in advance