You've somehow created a git repo inside another, git considers this to be a submodule, e.g. a pointer to another independent git repo. I kind of doubt you intended to do that, instead I suspect you merely wanted to add files to your original repo. If so then get rid of the submodule and just add normal files to the toplevel repo.
Submodules are useful when your project references specific versions of other (independent) projects and you want to include those specific version in your project. You can do this with submodules, and git can then track and checkout those other repo's (submodules) when your parent repo is checked out. You can interact with submodule repositories from the parent repo with the "git submodule" command.
Edit: Responding to the additional question in the comment below about how this happened and how to prevent it happening in future:
Obviously I'm guessing here, but I think what's happened is something like this:
1.) You created a repo, called "client", something like the following (I'm outlining the events using command line commands, I hope this is clear enough to communicate the gist, if not then ask for clarification):
mkdir client
cd client
git init
notepad somefile.txt
git add .
git commit -m "added somefile.txt"
cd ..
2.) Then you created another repo alongside that, called "server", again, similarly maybe something like this:
mkdir server
cd server
git init
notepad server.txt
git add .
git commit -m "added server.txt"
cd ..
At this point you would have had 2 independent repos alongside each other.
3.) Then I'm guessing you decided to put these into one containing folder "parent", and to make a repo out of this also (to maybe upload to github):
mkdir project
mv client project
mv server project
cd project
git init
git add .
Now notice what you've done: You've got 2 git repos already, now you've moved them inside another one...
But, you think, I need to add my 2 folders into the new parent repo.
So consequently at this point you'll get:
C:\temp\project> git add .
warning: adding embedded git repository: client
hint: You've added another git repository inside your current repository.
... etc
The key thing to understand is that when you have a git repo inside of another, it is considered to be a submodule, which means that the parent git repo will not track changes underneath a child git repo. The child repo will track such changes.
What you're really doing then, is trying to merge 2 independent repositories which remember, have independent histories...
How to deal with this depends on what you want. If you don't care about the commit histories in the original repos, you can convert them into normal folders (lose their repos, held in the hidden .git folder in each) before adding them into the parent repo by deleting the .git folder in sub folders.
Deleting the .git folder will delete the local repository copy of those folders, including all branches and all history. If you have no other (remote or backup) copies of your repository then this will mean all history/branches for these repos will be lost. Make sure this is what you want. You have been warned.
(It is advisable to make a backup copy of the original folders before doing anything.)
If you do this before you "git add" the moved folders into the parent repo you won't get the message anymore.
If you do it afterwards, you can still remove the .git folder to "fix" things, but you'll need to also make git forget about the child git repo/submodule (using e.g. the command "git rm --cached ..." -- see below.)
If however you want to retain the histories of both branches, effectively merging them as though they've always been one, then it is a bit more tricky. Again what to do depends somewhat on what you want as the output, but basically you need to create a new repo, set up the one original repo as upstream, pull all the commits from it, move the files into a suitable subfolder, then repeat the process with the other. There are multiple pages on the internet about this.
Probably what you'd want to read in that case is this question: Merge git repository in subdirectory and in particular the answer using git-subtree, which is the git command specifically intended for this sort of thing. Also this: How to un-submodule a Git submodule? -- It contains explanation regarding using "git rm --cached" to make git forget about a child folder being a submodule/repo in order to enable you to add it to a parent repo.
