multiple values of several fields grouped together I am using drupal 7 as a backend, in which I have a content type called conferences, and each conference has several events. I do not want to create another content type for events and would want to add them to the same content type as each event has only two fields the date and the venue. How can I achieve this using UI as CMS ? and then later be able to make API's to send the same. Please suggest modules to achieve the same
You should look at field_collection module. It allows you to create a field, and add fields to that field (behind the scenes it's using entities).

A typical use case, is if you want user to enter multiple sets of data, like fx


name
image
url


To achieve this, you would create a field_collection field on the node or what you want this on and set the cardinality to the limit. Then on the field collection you would add the name, image and url fields. It's also possible to configure some fields to be required and other to be optional.