Do you sell the iMac with 1 or 2 TB

Looking at the Apple Store page for the 24" M1 iMac, it appears that the custom-order storage options are

• 256 GB / 512 GB / 1 TB on models without USB3 and Ethernet ports
• 256 GB / 512 GB / 1 TB / 2 TB on models with them

One could also attach external drives (e.g., to supplement the internal SSD with much larger external HDDs).

1 or 2 Tb of what? Memory? Storage?

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Select and read the the purchase options.

No one here is an Apple employee, just users like yourself. You are not speaking to Apple here.