Now a days handheld devices offer assistant for your mobile device, which help users to do stuff easily and quickly, as you may know iOS has Siri (by Apple) and Android OS uses Google Now assistant (by Google) to facilitate its users. They are pretty much intelligent personal assistants and knowledge navigator which works as an application for their Operating systems.
Here comes another feature to Linux "Betty" as personal assistant, it uses natural language to answer questions, make recommendations, and perform actions. It is similar to Siri and Google Now but for now it is pretty much limited (it's still extremely useful and easy to use). It is a virtual assistant with a command-line-controlled natural language interface that uses sequential inference and contextual awareness to help perform personal tasks.

Things Betty can: You can do pretty much all sort of things, change configurations, find files, download files from Internet or do Internet queries, file & directory operations like compress/decompress and others, control audio applications, count words in a file, and many more...

Some Examples in Screenshots:

Further you can read documentation for supported commands.

To install Betty Assitant in Ubuntu/Linux Mint open Terminal (Press Ctrl+Alt+T) and copy the following commands in the Terminal:

Also turn on web mode for Betty (For Internet queries):
That's it