Simple question about 'Error'

Alright so question, when I join a server and Gmod starts downloading all those custom items, I still end up with a bunch of ‘Error’ symbols everywhere. But I was wondering, is it because my Gmod downloaded the items wrong or am I simply missing some major addon that would reveal all those Errors.

It is either an addon, or a game.

The “Errors” are caused by the server having models which you do not have installed onto your garrysmod. They are also caused by you not owning a game which the map or server is using.
You can ask the server player what the models were then search for them on (

The majority of players have PHX and Wiremod which use SVNs. (Explained here

Basically it means the server has a model (From an addon or game) which you do not have installed.

Helpful links: