Metadata can be defined as the sum of all your keywords/text and provide information about your app.
The relevant metadata fields for Google Play are:
Title (30 characters)
Short description (80 characters)
Long Description (4. 000 characters)
The relevant metadata fields for iOS are:
App Name (30 characters)
Subtitle (30 characters)
Keyword Field (100 characters)
Including your keywords in those metadata fields helps you rank higher on the used keywords and increase your visibility in the app stores.