OpenAPI 3.0

Info
Servers
Security
Paths
Path Item
Summary and description
Operation (GET, PUT, POST, etc.)
Request
Responses
Tags
External Docs
Components
Definitions
Responses
Parameters
Response Headers
Security Definitions
Callbacks
Links

AsyncAPI 2.0

Info
Servers (hosts + security)
Channel
Channel Item
Operation (Publish and Subscribe)
Summary, description, tags, etc.
Message
Headers
Payload
Id (application identifier)
Tags
External Docs
Components
Schemas
Messages
Security Schemes
Parameters
Correlation Ids
Operation Traits
Message Traits
Server Bindings
Channel Bindings
Operation Bindings
Message Bindings