For all intents and purposes, you need to join a server that has that pack installed.after more playing and researching... I'm thinking of switching servers. if I'm using a mod pack (still FTB Lite 3), do I need to join a server that has that particular pack enabled, or does a server just need to have mods enabled in general? or does it not matter? let me know if this question doesn't make sense, I'm still figuring stuff out here...
There are some mods which are "client side only" which can differ, but most mods have both client and server components.
Client-side only mods would be things that impact only you, such as fps-improving mods.