With the GM being the players' eyes and ears into the world, an important part of the game is what can be summed up as "gathering information".
Any time the players are asking the GM for information about the world, they are gathering information. There are a few different types of this:
Players can be asking for more details of either their immediate surrounding or the world at large, which to their characters are immediately obvious or are general knowledge.
Examples:
This kind of information gathering is a simple exchange between GM and player and requires no rolls. It is used whenever there is no uncertainty or risk involved with gathering that information.
The next type of information gathering is when the characters are digging for the non-obvious. They might be questioning NPCs and you don't want to play it out in full, or they might be searching in a library, or checking for clues in a location.
This type involves some element of uncertainty. The characters might miss some clues, nor not ask the right questions to the locals, or for some other reason find out only partial or even get misleading information.
Examples:
For this kind of information gathering, use Fortune Rolls, most likely using either the mental or the social ability, depending on how the characters go about it.
A fortune roll is used because there is no risk in the action, and the worst that can happen is that the characters come up with no or false information, but there are no immediate consequences.
The very act of gathering information can also in itself be risky, such as asking around about a criminal, or partaking in court intrigues.
This type involves not just uncertainty, but also risk, i.e. a failure carries consequences.
Examples:
For these, use standard Action Rolls to resolve them, with consequences and everything.
Another type of information gathering is the one that takes a really long time to complete, such as doing a thorough study of a subject in a large library, or questioning a large number of NPCs over a large area (a whole city or several villages).
This type of information gathering, where the main question is how long it will take, can be handled as a Downtime Activities > Long-Term Project.