What is Base64 part in Base64.encode

[zabruk70 via Digitalmars-d-learn]

I look to std.base64 module source.
And dont unerstand what is the "Base64" part in 
"Base64.encode(data)" example.
I see std.base64 module use template Base64Impl.
I see alias Base64 = Base64Impl!...
But down understand.
Base64 not module, not structure, not class?
Template Base64Impl shoud produce function?

I want create base32 encoder/decoder for example.
But i dont need template.
So how i can write Base32.encode()?
By creating class Base32 with encode() member.
By creating structute Base32 with encode() member.
Any other options?

Thanx.