When inplace=True is passed, the data is renamed in place (it returns nothing), so you'd use:
df.an_operation(inplace=True)
When inplace=False is passed (this is the default value, so isn't necessary), performs the operation and returns a copy of the object, so you'd use:
df = df.an_operation(inplace=False)
It simply means do not use any extra memory for replacement and replace and make changes in the existing data frame only. This is the case when inplace=true
One way is to do create a copy and make changes to the copy. This is the case when inplace=False