What does "only when sourcing script" mean?

## Steps to reproduce

> curl -sSL https://raw.githubusercontent.com/dotnet/cli/rel/1.0.0-preview2/scripts/obtain/dotnet-install.sh | bash /dev/stdin --version 1.0.0-preview2-002996 --install-dir ~/dotnet
## Expected behavior

I understand messages that it prints.
## Actual behavior

> dotnet-install: Downloading https://dotnetcli.blob.core.windows.net/dotnet/preview/Binaries/1.0.0-preview2-002996/dotnet-dev-centos-x64.1.0.0-preview2-002996.tar.gz
> dotnet-install: Extracting zip
> dotnet-install: Adding to current process PATH: /home/bb/dotnet. Note: This change will be visible only when sourcing script.
> dotnet-install: Installation finished successfuly.
## Environment data

`dotnet --info` output:

```
[bb@bb-centos72-3 ~]$ dotnet --info
-bash: dotnet: command not found
```

Or, more usefully:

```
[bb@bb-centos72-3 ~]$ ./dotnet/dotnet --info
.NET Command Line Tools (1.0.0-preview2-002996)

Product Information:
Version: 1.0.0-preview2-002996
Commit SHA-1 hash: cff4f37456

Runtime Environment:
OS Name: centos
OS Version: 7
OS Platform: Linux
RID: centos.7-x64
```