Import export – Difference between the field and the field storage in the configuration type?

I am exporting a content type and a field associated with the synchronization option available in Drupal 8. I exported and imported the YAML code for the content type correctly. When I was about to do the same for the field, I noticed a & # 39; storage field & # 39; in the type of configuration. What is the difference between the type of configuration & # 39; field & # 39; and & # 39; field storage & # 39; and do I need to export the corresponding code to both types of configuration? Below is the configuration file for the same field: & # 39; field_countries & # 39;
The field storage configuration is as follows

uuid: 2dbe8304-1cdf-4c11-8b2c-09e2a8e59213
langcode: in
state: true
dependencies
module:
- node
id: node.field_countries
field_name: field_countries
identity_type: node
Type: chain
adjustments:
length_max: 255
is_ascii: false
case_sensitive: false
Module: core
blocked: false
cardinality: -1
translatable: true
Indexes: {}
persist_with_no_fields: false
custom_storage: false

The field configuration is as follows

uuid: 74ef1365-f21e-4ac4-9ac3-de208d8ba96b
langcode: in
state: true
dependencies
config:
- field.storage.node.field_countries
- node.type.bookshare_title_metadata
id: node.bookshare_title_metadata.field_countries
field_name: field_countries
identity_type: node
package: bookshare_title_metadata
label: countries
description: & # 39; & # 39;
required: false
translatable: false
Default value: {  }
default_value_callback: & # 39; & # 39;
Configurations: {}
Field type: string