The addon was created originally for the sole reason that I was not able to find relevant buffs in the standard user interface.
The main use of the addon can be described quite easily: It reminds you about buffs and/or debuff which need renewal. If we go a bit more into detail, you'll find that the addon has grown quite a lot over time and offers a lot of functionality:
Notify the player if a buff is missing (including buff food, temporary weapon enhancements and much more) on himself
Notify the player if a certain buff on himself is almost running out and needs refreshing
Notify the player if a certain buff on his target is missing or almost running out and needs refreshing
Handles buffs cast by yourself as well as by other players
Notify the player if a debuff is missing on the current target (player or npc/boss)
Notify the player if a debuff (or curse) has been placed on him (by another player or npc/boss)
Notify the player about cooldowns which are available
Notify the player about abilities running / buffs active due to a cooldown being used
Maintain a list of the last couple of debuffs which affected the player
You can use the addon more or less out of the box with the only need for setup being that the addon needs to learn the buffs, debuffs etc. it can track and you telling the addon which of these are important. However there are many settings to adjust the addons behaviour exactly to your personal needs.
All the above can be configured in sets. Each set defines a list of buffs, debuffs and cooldowns you want to have watched. You will probably want a different set for each of your six roles. But you could also setup even more sets for very specific purposes. As there's no limit to the number of sets you can have as many as you want.