Just a bit confused as the PHB states that Druidic is used to write in code. Does that mean that Eyes of the Rune Keeper will allow me to read Druidic but not understand what it means or could I read it and understand it?
Eyes of the Rune Keeper does allow you to read Druidic (if you can spot it)
Druidic is a language, not a code or cipher
You speak Druidic, the secret language of the druids. You can speak the language and use it to leave hidden messages. You and others who know this language automatically spot such a message. Others spot the message's presence with a successful DC15 Wisdom (Perception) check, but can't decipher it without magic.
The only reason the messages are referred to as hidden and secret is that the language is because people who don't know Druidic find it hard to spot and can't decipher it without magic.
You need to pass a check to spot the writing first
[Creatures that don't know Druidic] spot the message's presence with a successful DC15 Wisdom (Perception) check, but can't decipher it without magic.
Since you don't know Druidic, you must pass a check to even notice the writing. Note how spotting and deciphering are two different things in the description above. Once you spot it, the Eyes of the Rune Keeper kick in.
Eyes of the Rune Keeper is magical and allows you to read the writing
The description for all eldritch invocations says:
In your study of occult lore, you have unearthed eldritch invocations, fragments of forbidden knowledge that imbue you with an abiding magical ability.
Eyes of the Rune Keeper, a magical ability by virtue of being an eldritch invocation, says:
You can read all writing.
Thus, if you are able to spot some Druidic writing, you would be able to read it with Eyes of the Rune Keeper.
Yes. Druidic is a language. It's not a cipher
Eyes of the Rune Keeper allow you to read any written language. As long as the meaning of the language is plain, and not a cipher, the character should be able to comprehend it.
The druidic language is specifically called out as being decipherable by magic such as an eldritch invocation.
Others spot the message’s presence with a successful DC 15 Wisdom (Perception) check but can’t decipher it without magic.