Sharepoint SPField InternalName vs DisplayName

Following is the list of common spfieldcollection/spfield methods
and name they require (Display Name / Internal Name).

• SPFieldCollection[name] : SPField
  name: DisplayName
  
• SPFieldCollection.GetField(name) : SPField
  name: internalName, displayName or internalName and displayName from the current context
  
• SPFieldCollection.GetFieldByInternalName(name) : SPField
  name: internalName
  
• SPFieldCollection.ContainsField(name) : bool
  name: displayName or internalName
  
• SPListItem[name] : object
  name: internalName, displayName or internalName and displayName from the current context
  
• SPListItem.GetFormattedValue(name) : string
  name: internalName, displayName or internalName and displayName from the current context