There are three main ways that metadata can be used in Salesforce Apex to complete the necessary processes: by importing the metadata into Salesforce, by updating it in the product’s interface, or by using the Salesforce metadata API.

Salesforce Metadata API explains how salesforce.com and Force.com development artifacts are structured. With Force.com, you only need to code as opposed to the customary development process of code-compile-package-deploy.

What is Salesforce Metadata?
Metadata is a simple lightweight language which based on XML. Salesforce metadata are parts of Salesforce that define how objects behave and how your org looks ,metadata are the “nuts and bolts” of your Salesforce org.

You may assume that metadata and data are the same – they are not.

• Data relates to the records that a business relies on, e.g. users, Accounts, Contacts, etc.
• Metadata is the data that describes data, the way that records behave and the “look and feel” of your Salesforce org.

Hard-coded applications are a thing of the past – configuration is the flair of the season.

Organisations need flexible applications that can be tailored to what their business requires, without needing high-level programming skills. Metadata is what transforms Salesforce from a simple database into an entire platform – that’s why Salesforce metadata is so powerful.

Salesforce Metadata API is used to manage our application customisation programatically as well as export and migrate meta data. Force.com Migration tools uses Metadata API to retrieve and modify our organisation structure. Salesforce.com has made this asynchronous API available to users so that you can build your own client applications on top of it.

Salesforce users frequently ignore the extensive range of Salesforce metadata. Whatever your position, it’s critical to comprehend the distinction between data and metadata. Your metadata supports a number of daily business operations and contains important information about your Salesforce org. Therefore, it needs to be handled carefully.