Opening an Application via Terminal [duplicate]
You can just type the the name of the application you want to start. In your case it would be libreoffice or if you want to go to writer directly you can type libreoffice --writer
If you do not want the application tied to a controlling terminal you can type the application name followed by & disown.
In @Germar's example the full command would read libreoffice & disown. This would enable you to close the terminal you launched from, and continue using libreoffice.