Problem with installing rvm

Question

I try to install rvm on Ubuntu 14.04.

$ \curl -L https://get.rvm.io | bash -s stable --ruby
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   184  100   184    0     0    843      0 --:--:-- --:--:-- --:--:--   847
100 22817  100 22817    0     0  47846      0 --:--:-- --:--:-- --:--:-- 47846
Downloading https://github.com/wayneeseguin/rvm/archive/1.26.10.tar.gz
Downloading https://github.com/wayneeseguin/rvm/releases/download/1.26.10/1.26.10.tar.gz.asc
gpg: Signature made Mon 02 Feb 2015 11:09:00 AM EST using RSA key ID BF04FF17
gpg: Can't check signature: public key not found
Warning, RVM 1.26.0 introduces signed releases and automated check of signatures when GPG software found.
Assuming you trust Michal Papis import the mpapis public key (downloading the signatures).

GPG signature verification failed for '/home/t/.rvm/archives/rvm-1.26.10.tgz' - 'https://github.com/wayneeseguin/rvm/releases/download/1.26.10/1.26.10.tar.gz.asc'!
try downloading the signatures:

    gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3

or if it fails:

    command curl -sSL https://rvm.io/mpapis.asc | gpg --import -

the key can be compared with:

    https://rvm.io/mpapis.asc
    https://keybase.io/mpapis

I then run what it sugests:

gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3

and then rerun

\curl -L https://get.rvm.io | bash -s stable --ruby

Now it seems working.

1. What does the problem mean, and what happens when I run the gpg command that solves the problem?

2. why is there \ in front of curl?

Thanks!