Cspath-python-strings/projects/thread-shed

In the python project “Thread Shed” I am having trouble understanding how the nested for loops work.
Can someone explain to me what each line is doing in english?

[python]
transactions_clean = []
for transaction in daily_transactions_split:
  transaction_clean = []
  for data_point in transaction:
    transaction_clean.append(data_point.replace("\n"," ").strip(" "))
  transactions_clean.append(transaction_clean)
[/python]

Thank you