Check out example codes for "rails form_tag". It will help you in understanding the concepts better.

Code Example 1

form_tag('/posts')
# => <form action="/posts" method="post">

form_tag('/posts/1', method: :put)
# => <form action="/posts/1" method="post"> ... <input name="_method" type="hidden" value="put" /> ...

form_tag('/upload', multipart: true)
# => <form action="/upload" method="post" enctype="multipart/form-data">

<%= form_tag('/posts') do -%>
  <div><%= submit_tag 'Save' %></div>
<% end -%>
# => <form action="/posts" method="post"><div><input type="submit" name="commit" value="Save" /></div></form>

<%= form_tag('/posts', remote: true) %>
# => <form action="/posts" method="post" data-remote="true">

form_tag('http://far.away.com/form', authenticity_token: false)
# form without authenticity token

form_tag('http://far.away.com/form', authenticity_token: "cf50faa3fe97702ca1ae")
# form with custom authenticity token

Learn ReactJs, React Native from akashmittal.com