The "fold level" is the depth of the fold:
1
2
3
The line that you put in your ~/.vimrc
,
set foldlevelstart=1
tells vim fo close every fold up to level 1 by default.
Set it to an impossibly high value to open all folds by default:
set foldlevelstart=999
Note that you can also try a low level like 2
or 3
which may have interesting results depending on your coding style.
See :h foldlevelstart
.