Visual Studio creating multiple/ additional worksp

I started using TFS since VS2010. By that time I already created my own TFS server (myname.visualstudio.com). My problem is that I created a new project on the my TFS website (the one with the dashboards). Then when I go to VS2017, and connect to that new project, it asks me to map and get it as expected. Instead of just clicking "Map & Get" button, I instead clicked advanced so that I can configure everything.

On the workspace configuration dialog, I noticed that VS names it as "MYPCBLABLA_1". If I try to remove the "_1", VS says that "the workspace blablabla already exists on computer blablabla", and does not let me use my existing workspace name.

Why does it do so? Can I not use only 1 workspace? From what I understand of workspaces, it is the container of my projects, so different workspace, different set of projects. But what are they really?

Additional info: I don't know if this helps but on the past, I used to format my PC many times, I'm not sure if that affects the mappings or workspace names when I use VS after reformatting.

Workspaces are maybe the least well-understood feature in TFVC. And you are right in saying they're a way to isolate different sets of files from a TFVC repository.

A lot of people configure a new workspace for a specific project or set of solutions, but let's look at some of the ways workspaces can be used in detail:

Hotfixes: you may need to create a hotfix for something happening now, but you have pending changes in your existing workspace. Instead of shelving these changes, performing a "Get Specific version" on the bugged version, you can also create a new workspace in which to solve this particular problem. After completing the fix you can then continue working with the other workspace without needing to do anything.
Experiments: you may want to do some major refactoring, restructure source control or some other highly impactful operation. Doing this in a new (temporary) workspace helps you prevent messing up your normal work area.
Reviewing other peoples changes: When performing a review on another person's changes, you may want to have a local copy so you can run, annotate and play with the other person's code. Instead of taking these changes into your own workspace, you can easily bring these into a temporary workspace, which you can safely delete afterwards.
Performing a merge, while you are working on other changes: It may be the case that you're working on a new feature an already have some changes merged back to another branch when a release needs to be shipped. In order to prepare this release, without picking up changes or overwriting work in progress in your current workspace, it's often easier to perform these kinds of release activities in a temporary workspace, that way you know that the work is always done on the exact version in source control.
Preventing accidental changes to important branches: By putting your production branch in a separate workspace, you can't accidentally combine changes from say Development and Main into a single check-in. Since Visual Studio often auto-selects all pending changes in the workspace, this may cause unintended changes to your master/main branch. I've written a Check-in policy to prevent these issues, but having separate workspaces is a much safer solution.
Working with multiple developers on the same workstation/server: in some organisations, developers use a remote desktop to a central beefy server to do changes. To ensure each developer has his own set of files, each developer gets his/her own workspace. An alternative is to make the workspace public, which allows multiple developers to use the same workspace folder. But this often leads to all kinds of unexpected issues.
Browsing an old version of the code: if you need to review/compare an older version to a new one, you can often get away with the folder diff view in Visual Studio, but if you need to do more thorough comparisons, you may want to have 2 copies of the same folder in your TFVC repo. Creating two workspaces will allow you to have two different versions of the same folder on your local disk.
Prepare a special version for merges or labels: You can merge and label the workspace version of a set of files. You can create a workspace and then use Get Specific Version to fetch specific versions of specific files, these can all come from different changeset versions. Once you're satisfied, you can perform the label or merge or branch action to store this specific workspace version configuration on the server.

As you can see, Workspaces allow you to do parallel development on one machine, isolate changes etc.

Be creative

As you can see, workspaces are a very powerful concept. Usable for a lot of operations. But you need to understand the concept thoroughly. Many developers don't understand exactly what workspaces are and how they work, they're missing out of some of the most powerful concepts of TFVC.

Consolidating and cleaning up

In your case you now have to workspaces. In order to consolidate these (if you want to), you can unmap the folders from your _1 folder and then map these same folders in your original workspace. You can also delete the _1 workspace from the TFS Server and then update the mappings of the original workspace.

Remember that workspaces are stored on your local machine, but that the TFS server also has a registry of who mapped which TFVC folders to which workstations. So simply deleting files from your local disk is not sufficient. You need to save these changes to the TFS server (this happens automatically after performing a get operation after changing the mappings).

To check which workspaces are registered to your workstation on the TFS server, use:

tf vc workspaces /computer:YOURWORKSTATIONNAME

Then delete old workspaces with

// DELETE the local workspace
tf vc workspace /delete:WORKSPACENAME

// DELETE the workspace registration on the TFS server
tf vc workspaces /remove:WORKSPACENAME