like on windows that we compress files with the format .zip , in linux the format will be .tar.gz
so for uncompress it you need to

tar -zxvf  youfilename.tar.gz

or if it’s only .tar you can open it with:

tar -xvf  youfilename.tar

or if it’s compressed with tar.bz2 use:

tar -jxvf  youfilename.tar.bz2

it will give you a list of all files and folders that has been extracted and next time you go to that directory you will see 2 file. one that you already had with tar.gz and a new one that’s uncompressed.