Computer disks have a finite capacity, and when they fill up it can lead to serious problems, including lost data and email. Actually it's slightly more complicated than that; disks are divided into partitions, and the problems ensue when an important partition such as one containing user files fills up.
Here is the different types you can check your disk space in your ubuntu system
Using Disk Usage Analyser
The utility will give you both a text version of the space and a graphical representation of the data that is on your hard drive.
If you want to open this go to Applications--->Accessories--->Disk Usage Analyser
Once it opens you should see the following screen
Using df command
The df command displays information about total space and available space on a file system.
Here is the example using df command
If you want to know more available options check df man page
Discus is a GPL text-mode disk space usage program.Discus aims to make df prettier. Features include color, bar graphs, and smart formatting of numbers (automatically choosing the most suitable size from kilobytes, megabytes, gigabytes, or terabytes). Or choose your own size, along with specifying the number of decimal places.
Install Discuss in Ubuntu
sudo apt-get install discus
and press enter this will complete installation after this if you want to use discus check the following example
A screenshot with the default settings
If you want more available options check man page