Depends on the project and where you get assigned. Your team lead will (hopefully) let you know and you can usually rely on your seniors to tell you what to do (or if they don't, then just pester them once a day ~ every few days).
If they tell you there's nothing at the moment, then it's up to you : If you're at home, do what you want. Or (mainly if you're at the client place) 'pretend to look busy' and try to understand more about the project with little to no guidance, then compile your questions to ask when they're free. xD
Unfortunately, there's going to be a lot that isn't explicitly or directly told to you, usually until the last minute. Or who knows, maybe your seniors/leaders will be more helpful than mine and can tell you what's the overall plan and what you'll be doing over the next few weeks ~ months instead of it being like
NS where you only know what you'll be doing tomorrow during the night briefing.
My current project is a weird adaptation / balancing act that can be summed up as everyone just takes it easy and goes with the flow. So my batch kind of feels when we have to leave the project or company, we'd have to learn how to re-adapt to a more proper environment because we might get too complacent here. Like even poly/uni feels more structured than what we've got right now, in terms of knowing what we're doing and going to be doing in the future. xD