Aliases can be global, i.e. apply by default to every user on the system.

However each user can also have their own aliases which only apply to them.

Local aliases are specific to the user.

These aliases should be defined in a file named .bash_aliases user's home directory.

~/.bash_aliases

alias apt='sudo apt-get'
alias update='sudo apt-get update && sudo apt-get upgrade && sudo apt-get autoremove && sudo apt-get autoclean'

To apply the changes immediately to your bash profile without having to log out, simply run this:

. ~/.bashrc

or

. ~/.bash_profile