Hi @Ashish_Eclerx ,
1) Usually the development team will be having three environments Dev, QA, PROD.
Dev --> For developing and testing the initial level changes
QA --> After completeing all the development, the website will be moved to next(QA) environemt, where the Quality assurance team will conduct their testing and will give their sign off.
PROD --> After getting sign off, webiste will be moved to PROD, where customer facing.
In the above cases, Tealium is already having environment named as dev, qa and prod. So we can copy and pase the tealium code in the respective environment.
In somecases, client may be stating that before pushing the changes as customer facing (PROD), they need to do some regression testing other than DEV and Stage.
A replica of PROD(preprod) environemt. In this case you may need to create and use the custom environment.
2) You are having different GA Ids or Adobe Analytics Report suite for each environment, DEV, QA, PROD, PREPROD. Then in this case also you can use the custom environemt.
Also refer this : https://community.tealiumiq.com/t5/iQ-Tag-Management/Custom-Publish-Environments/ta-p/13630