I think it depends on context - I'm guessing you're thinking about flow of funds where as others are thinking about the actual process of running ACH files through the network.
As an end consumer or other entity(like a TPA or bank ISO), you can submit a request or set of requests that will end up in that banks ACH file. At the end of the day, the bank that submits that file is responsible for ensuring those requests are valid, and ensuring all the returns are processed. These requests consist of to/from account routing information and dollar amounts with a lot of other rules in the file specifications. Not every banks can submit these directly. A lot of banks submit to larger banks and so on. I vaguely recall there also being fines/fees applied to the file submitter on if you send bad data or exceed return thresholds.
As an end consumer or other entity(like a TPA or bank ISO), you can submit a request or set of requests that will end up in that banks ACH file. At the end of the day, the bank that submits that file is responsible for ensuring those requests are valid, and ensuring all the returns are processed. These requests consist of to/from account routing information and dollar amounts with a lot of other rules in the file specifications. Not every banks can submit these directly. A lot of banks submit to larger banks and so on. I vaguely recall there also being fines/fees applied to the file submitter on if you send bad data or exceed return thresholds.