By hand vs manually ?
What's the differences between "by hand" and "manually"?

Here I copy the sentence as below. Would you like to help me on my this confusion?

We use computers to automate solutions to problems and to do things faster and more accurately than we can do by hand or manually.

Question

By hand vs manually ?
What's the differences between "by hand" and "manually"?

Here I copy the sentence as below. Would you like to help me on my this confusion?

We use computers to automate solutions to problems and to do things faster and more accurately than we can do by hand or manually.

Answer

The author is implying that computers/machines will soon be able to automatically perform human functions such as typing on the keyboard, clicking buttons using our hands OR visually measuring thermostats MANUALLY to make sure that a nuclear reactor doesn't overheat.