The content inside the backticks are tags:
A field declaration may be followed by an optional string literal tag,
which becomes an attribute for all the fields in the corresponding
field declaration. The tags are made visible through a reflection
interface and take part in type identity for structs but are otherwise
ignored.// A struct corresponding to the TimeStamp protocol buffer. // The tag strings define the protocol buffer field numbers. struct { microsec uint64 "field 1" serverIP6 uint64 "field 2" process string "field 3" }
See this question and answer for a more detailed explanation and answer.
The back quotes are used to create raw string literals which can contain any type of character:
Raw string literals are character sequences between back quotes “.
Within the quotes, any character is legal except back quote.